Hans, I am having a very similar problem intermittently. It first started soon after I installed Win 7 ten days ago. I would find the monitor suddenly shutting down into sleep mode while I was using the computer and I could not wake it. Sometimes there would be a BSOD, but mostly not. I cannot remember the exact details of the report I was getting, but I know Windows minidump was mentioned, same as your report. Windows suggested updating my mouse driver, a Microsoft Intellimouse, but the problem persisted. It also suggested updating my Radeon 4670 Catalyst driver. The version Windows installed was dated August, but I found one dated September, so I installed that, but it made no difference. Then I noticed that the problem occurred mainly when using the mouse scroll wheel, so I disabled it and the problem went away for a couple of days. I thought it was solved, but yesterday when I was going through my photo collection and clicking on thumbnails to enlarge them it began crashing again but this time the system would reboot itself rather than me having to restart it.
I know my BIOS is out of date, but I know someone with the same mobo and BIOS version as mine, and he doesn't have any problems running Windows 7, so I doubt it is that.
I believe this is either a graphics problem which might be sorted out in a future driver, or down to my Ram, which is the lowest reading on my Windows Experience Score, at only 5.5. I don't know if any of this is similar to your own experience.
My system is:
Windows Home Premium retail
ALiveSATA2-GLAN mobo
AMD64x2 6000
Radeon 4670
2 x 1gig cheap DDR2, not a matched pair so not running dual channel (could be my problem)