This is infuriating me. To set the stage: songs that have been on my computer for years; new songs/albums just added to library; everything of the particular artist is deleted; nearly duplicate itunes libraries on mac and windows, windows itunes is working fine; So this is the rundown. A song is playing, with all songs of a particular artist in the queue. I click to play another song. It starts playing but an exclamation mark pops up next to a different song to indicate the file is missing. I open the itunes media/music folder and sure enough that artist's entire folder is missing, yet the current song is still playing. Trying to play any/every song from that artist follows with the "file can't be found." Even restarting the currently playing song leads to this. I also notice it when importing songs, be it downloads from amazon or elsewhere, or even from my windows itunes library from the home sharing import button. One album can exist in the mac itunes library, but as soon as I import another album everything disappears, including what had been there previously and that which I had just tried importing. Every time the current song playing continues to play, despite disappearing from the itunes media/music folder. This seems random, but once it starts with a particular artist, it keeps happening, *almost* repeatedly. It seems like certain songs may be like a trigger that causes it. Previously, playing one particular song, and only that song, would poof the particular artist's catalogue. I just reripped that song and everything was fine. Now it seems like any random artist and any of that artists songs. Deleting everything and reimporting leads to the same problem all over again. These songs have been playing in itunes, ipod, iphone, and earlier itunes fine. I think the last reversion of itunes 9 may have been when I first started seeing this, and its only getting worse, fast. On windows, itunes is acting its normal self.. All albums coexist with each other, no songs disappear without warning, playing a certain song doesn't cause all songs to disappear without warning. I haven't seen anything like this before and I can't find any recounts. It really reminds me of the iphoto '11 debacle. Oh, and &#%#$**@#%#$%^&*$^&*% Any explanation to this insanity?