must admit i'd forgotten about this when proclaiming my 3 years free of ati trouble earlier. it is quite a major issue.
basically you get random driver crashes with vista aero enabled on dual screens. it randomly happens across all cards and any drivers since vista came out. (well up until last year at least- after i got rid of my 2nd screen i didn't keep upto date with what was going on)
i think the problem may be if you have 1 dvi and 1 vga monitor. i think people with dual dvi are ok.
it has to be a driver problem because putting load on the card makes no difference. you can be gaming for hours and it's fine. then bam it'll happen on the windows desktop doing nothing. i simply ran vista without aero to get around it. pretty annoying though. obvious xp is unaffected and i have no idea about 7....