I really love my good old Droid, but every now and then it has this problem. Far less often now on rooted and overclocked/undervolted 2.2 than originally, but still happens every couple of days. The issue is that every music file I have on the device is in WMA format, and every couple of days or so both the stock player and WinAmp(beta) refuse to play any of them, including the file that was playing the last time. It says it can't play files of this type, and the only solution is to reboot the phone, at which point all is good. I've read somewhere that the Droid2 also had this problem and that Motorola was looking into it, but this is the original Droid. It seems to happen whether I shut down the music player myself or if it pauses playback when I unplug the headphone cable from my car stereo (yay for Aux inputs). Yeah I could convert all my files to mp3, but I currently keep all my music in WMA Lossless on my home server and transcode them down to 320kbps WMA for portability. Also, since the media services on my Droid seem to normally have no problem with the WMA format, I'm not even certain that making them mp3 would solve the issue.