There have been various reports of this occurring before, with version 3.x by other users. However, I believe those reports have MM always causing this to occur. That's not the case for me, and I've never had this occur with 3.x. The weird part about it is, you know what the action (seems to be) that MM performs to cause this? Idles. I'm not playing a large video file, or anything crazy like that when this occurs. Each time it has happened, MM has been sitting idle for some time. Something there seems to be in common though, is all three times I've seen this... that screensaver had activated and I was bringing it out of it (with required password).The color scheme has been changed
The following program has performed an action that requires Windows to temporarily change the color scheme to Windows Vista Basic.
Program: MediaMonkey - Audio Library
Publisher: Ventis Media, Inc.
Process Identifier (PID): 6524
Windows will automatically change the color scheme back to Windows Vista Aero when this program or other programs performing similar actions are no longer running.
I'm uncertain whether this should be classified as a bug, or just chalk it up to my system. However like I've said, I've never had this occur with 3.x, and given the circumstances behind it... I think it at least warrants a mention.
Beyond that, when Aero is disabled... MM looks... well, horrible. Doesn't seem to degrade elegantly. I don't know if this only happens because of the switch, or if this is how it appears with Basic (if so, poor souls).

Some stats: Windows Vista Home Premium (SP2), 1.86ghz processor, 2gb memory.