Jim Roseberry on here installs that interface in his job. You should contact him. You may need to pay for his time but that's between you and him.

My Mackie will occasionally change to a really high bitrate and I have to bring it back down to hear sound (using the Mackie control panel). I do run two sound cards, which I think is part of the issue for me.

Take a look at your screensaver too. Many come with audio and mess with resource allocation.

Don't have a screen saver, so I can rule that one out (just double checked to make sure).
 
Could look into it maybe being an IRQ conflict of some kind.
 
One note: when this happens, I can still hear my bass guitar when I have it plugged in. Like, if I'm running both my bass guitar and playing back audio from my computer, the computer audio will stop working but I'll still be able to hear my bass.

Today this happened while I was watching a video. In the middle of the video. Wasn't doing anything else.

FWIW, when I was running an M-Audio interface, I found its behavior with Win7 a bit flaky. I ended up using the onboard audio for Win7 only and that removed a lot of conflicts I was having. The downside of this is that it requires two sets of speakers. In order to get Win7 to lay off the audio interface, I had to power the interface on and go into "Change sound card settings" (will see both in there) and explicitly assign the onboard audio as "default." This removed Win7 from the loop with the interface, so if Win7 ever saw it power on/off, it would not try to hog or conflict with the drivers.

If you have both USB2 and USB3 ports, make sure the interface is plugged into a USB2 port.

@Scook: only USB 2 here.
 
@mettelus: I hope it doesn't come to that but it's looking like it might...