Are you able to try your card under XP via dual boot? I got the same issue (had two problems: I would get "Adapter has reset" under Vista, and would get a blue screen under Vista indicating a problem with "ATIKMDAG"). I did the same as you did; tried uninstalling the drivers using SkyMtl's procedure (
ATI HD4870 & HD4850 Crossfire Performance Review) , and I had the exact same issue under a couple differnt versions of Catalyst.
From the research I did, it was blamed on drivers or overheating hardware. I have been running the same card now under XP for anout 3 weeks with absolutely no crashes, so I think my hardware is fine. I crashed 1-2 every couple of days under Vista, even after a Vista fresh reinstall like you. Weird I know, as I had an nVidia card that never had a problem for months under Vista and the computer worked really well. Would crash when folding very often (gpu at 100%), but has held up fine when folding as well under XP.
So I would try reinstalling the latest drivers using Sky's procedure I linked to above. Works for some people. I never got my problem fixed under Vista, but XP seems fine now. Otherwise, try stressing out your card by using a gpu folding client or using Atitool (
ATITool - Overclocking utility for ATI and NVIDIA cards) to stress out your card to see if perhaps the hardware is wonky. I used XP to rule out hardware, as I assumed that my computer would crash in XP if there was a problem there.