Thanks for the information there,
Based on your experience, it seems even more likely that my video drivers might be causing these problems. It is a bit surprising that graphics issues could cause so many problems with audio, which, to me, seems somewhat unrelated hardware-wise. For the Thinkpad P70, in the BIOS, unfortunately I only have options to choose either discrete graphics only (the nVidia Quadro in my case) or hybrid graphics (nVidia Optimus I believe). Integrated only is not available to me, although I may be able to disable the Quadro GPU in the device manager. I will try that and see what the results are.

It seems that most of these Totalmix freezing problems are unique to Windows 7 x64 as well, from what I've read. I might try out Windows 8 or 10 on another partition and see if the problem persists, although it'd be great to solve the issue in Windows 7 instead, since installing another OS (and all of my recording software) is a somewhat time-consuming task.

The error that you see is most probably caused by the realtime level meters that TM FX shows. The transmission stops when all TM FX windows are closed/minimized. Nevertheless - the real error is not TM FX but your hardware which can not hold up a stable USB connection. Not TM FX causes the error, but it is the victim and the first sign that something is not as it should be. BTW, did you ever check for USB errors shown in the UFX Settings dialog?

@ Ramses: graphics problems with nVidia are not a general problem. In seldom cases a driver update fixed problems. Did you ever try the alternate graphics mode in TM FX preferences?

In the same way I can not confirm any problems working only with the Intel 530. I am doing this for some time now with my Dell XPS15, with phantasticc results (currently on a LG 3440 x 1440 screen via Thunderbolt, while using TB, USB3, USB 2 and FW at lowest latency).

As its my company notebook I deinstalled recording related SW some time ago. It was just a test for eventually buying one for private use. For testing purposes I installed now the lastest RME USB driver for UFX: v1.093, HW rev 357.
OS: Windows 7 SP1 x64 Enterprise
nVidia driver: 344.11 from 18.09.14.

Whats strange / new: I can not add Totalmix to the list of programs, to determine whether to use internal or nVidia Graphics ... I can "add" Totalmix and "Apply" ...
but when I close and reopen this screen (nVidia Control Panel -> Manage 3D Settings -> TAB "Program Settings")
then the Totalmix entry is gone (c:\windows\system32\totalmixfx.exe).
Sorry, I can't test this now for you. I fear the User Policies have been set even more restrictive though I am admin on this system. But I am pretty sure even those rights can be restricted by policy manager.

Strage that it was possible though, to add Firefox and to switch between using nvidia and internal graphics.

BTW: when I use the Intel HD graphics I get again audio drops with ASIO buffer size of 48 when scrolling up and down in Firefox Web pages with graphics in it, like i.e. heise.de. It goes away when running Firefox via nVidia GPU.

I have done a bit more testing, and found out a few interesting bits of information regarding this freezing issue:

I tried using a USB 3.1 port on the laptop (which, as far as I know, appears to use both different hardware and drivers from the standard USB 3 ports on the laptop), and the problem still persisted in the exact same manner. I also tried connecting the external monitor to a Displayport port, a HDMI port, and a USB3.1 to HDMI port, and all of them exhibited the same freezing. It is important to also note that the laptop must use the nVidia GPU in order to use any external monitor. The integrated Intel GPU only seems to work for the internal laptop display.

I did a bit more testing regarding the graphics, and found a few interesting details. In the Device Manager, I was able to disable the nVidia GPU, which forced the system to use the integrated Intel GPU, but when I did this, none of my external display ports were working. Since I use an external display for recording most of the time, this is not a good work-around. Another thing to note is that when I would disable that nVidia GPU, the Totalmix meters would show a quick 'pop' of levels as if I had restarted the interface itself.
What is very interesting is that, when re-enabling the nVidia GPU, Totalmix would freeze in the same manner as I have been trying to diagnose. To test the consistency of this, I tried it two more times, and every time I re-enabled the nVidia GPU in the Device Manager, the same exact freeze would happen. I have screenshotted the error (the meters shown in this screenshot are frozen, and not moving).

On the third time, the computer blue-screened shortly after. Here is a picture I quickly took of the error itself:

I managed to save the dump file from the blue-screen event as well. Here is a download link:

https://drive.google.com/open?id=0ByRtj … 2NzQnlBN0U

Since this problem has occurred on USB2 ports, USB3 ports, and USB3.1 ports, each with different drivers and hardware, but has not occurred on other brand interfaces, this definitely seems to be a graphically-rooted problem with Totalmix itself, specifically with the newer nVidia Quadro GPU's. I understand the Quadro GPU's are not as widely supported because they are less common than consumer GPU's, but this Quadro GPU has had good compatibility with all other software and plugins I have been using, and it seems to only be Totalmix that has trouble with it. The Quadro is the only thing that is quite different from the hardware mentioned above, and I think it is safe to assume that it narrows it down to the GPU. Unfortunately, many modern workstation laptops and desktops (which are otherwise very well-suited for recording use because of their power) have Quadro GPU's, so I hope to see a reasonable fix to this problem soon. I am going to test this on different Firewire expresscards, and I can post an update after that.

I apologize for the delay, because of the somewhat random nature of the bug, it has taken me a bit of time to test the things you have suggested. Here is what I have found out:

High performance mode is enabled, and has been the entire time, so that probably rules that out.

The error does not seem to happen on the Intel GPU alone, and also does not seem to happen while using the nVidia GPU only, but with the drivers uninstalled, and using the basic drivers, as you had suggested. I suppose this does not absolutely confirm that the problem could not have happened, since it is so random, but in about 2 hours of testing per scenario, I noticed no issues (With D2D on or off). Neither of these are an option for me since the external monitor ports do not work with either the nVidia GPU or nVidia drivers disabled, but it does perhaps reveal more about the nature of the issue.

I did notice, though, that when connected via USB, I had another, perhaps unrelated issue, regardless of graphics driver settings. The buffer size seems to become mismatched while switching audio programs, and I get a distorted, "sample-mismatched" glitchy sound until I go into the Fireface USB settings, change the buffer size, and then change it back again. Only then does it seem like the software "lock in" to the correct buffer size, and function correctly. It seems to affect recording as well as playback, and this problem was still present, requiring me to reset the buffer size every time I would switch sample rates. I think part of the problem is, when going from, let's say, 88k to 44k, Totalmix automatically halves or doubles the buffer size to maintain the same latency. The audio programs, though, do not usually do this. In Cantabile, for example (A standalone VSTi player), when switching sample rates, the software wants to see the same buffer size, while Totalmix switches buffer sizes automatically, and does not seem to correctly update the software to this switch. I have to manually reset the buffer size in the Totalmix USB settings because of this, which isn't a huge problem, but since I use hardware monitoring for recordings, it has resulted in me having to throw out a few good takes at the beginning of sessions because they record distorted due to a mismatch.

I did notice another interesting detail about this freezing problem. I tried purchasing a few Firewire expresscard adapters to test this out as well. I tried a Startech Firewire 400 card, a Siig Firewire 400 card, and a Startech Firewire 800 card. Both of the Firewire 400 cards did not work at all. The Startech 400 card resulted in loud, distorted cracking, constantly, every time I would initialize ASIO. The SIIG card just did not work at all, and no audio would play. (Both of these cards worked fine for an external Firewire hard drive that I tested). The Firewire 800 card, connected via a Firewire 800 to 400 cable, works great though.

Running the UFX via Firewire, I have not experienced any freezing problems at all, nor have I experienced any problems with buffer size mismatches. For now, this is my solution (although, for mobile recording, I still rely on a Babyface, which is unfortunately USB only, so I still have to be wary of freezing using this interface).

I'm not sure why the nVidia graphics drivers would only cause trouble with USB connections, but since the problem seemed to go away when I had entirely removed the nVidia drivers in one way or another, they still seem to be a culprit here.