Here is an explanation what happens:

1) When you disconnect the Multiface from the HDSPe/FW cable either while the Mac is awake or asleep the red HOST LED on the MF will blink. The same happens when you send the Mac to sleep while the Multiface stays connected. Whenever you reconnect/wake the system in this blinking state the HDSPe will correctly re-detect the MF.

2) When you turn off the MF and turn it back on while the Mac is *awake* and then turn it back on the red HOST LED will burn solidly for a second and then turn off. While the Multiface is disconnected/turned off the HDSPe driver still runs in MF mode and only reports it as disconnected (properly so).

3) When you send the Mac to sleep and disconnect/turn off the MF before or while the Mac is sleeping and awake the Mac with the MF disconnected/turned off (aka only HDSPe card present) the HDSPe driver will report as "Digiface".

When you connect the MF afterwards the driver will still stay in "Digiface" mode even after detecting the box.

4) When you turn off the MF and turn if back on while the Mac is *asleep* then the red HOST LED will burn solidly and keep burning until you awake the Mac. The HDSPe driver will first report as "RPM" and only then connect to the MF. Because of this order the driver will stay in "RPM" mode even after detecting the box.

Workarounds

A) While the Mac is awake and the MF connected plug out the HDSPe and plug it back in. This is what you are already doing atm. Using the "Power off card" function is not mandatory, but may prevent sporadic freezing of the Mac.

B) While the Mac is asleep plug out the HDSPe and plug it back in *after* the Mac is woken up. This saves you the use of the "Power off card" function and generally might be more healthy electrically.

C) After you reconnect the MF (red HOST LED off) and see the HDSPe report the wrong "RPM" or "Digiface" model, send the Mac back to sleep and wake it up again. Upon wake up the HDSPe driver will correctly run in "Multiface" mode because the box already was connected when you send the Mac to sleep (blinking HOST LED, see 1).

One quick question - in the workarounds, when you say "Plug out" do you mean turn the power off to the MF, or do you mean pull out the expresscard?

Just to stress this for anyone else reading: There are no problems when the Multiface is not turned off during when the Mac is asleep and there are no problems when the Multiface is turned off when the Mac is awake. Only the combination of turning the MF off while the Mac is asleep causes this inconvenience.

I'm always rather wary about the combination of audio and suspend/sleep modes. Too much can go wrong there and it should never be used right before a live gig. You won't grow old waiting a few seconds for your Mac to boot-up properly.

PS: I'm currently testing a new eSATA card that doesn't even support hot-plugging the card in while OS X is running, you need to plug it in before booting OS X (or use bootcamped Windows, which surprisingly works with hot-plugging the very same card in the very same Mac).