Windows 7: BSOD APC Index Mismatch 0x1 - please help

I have a Dell Vostro, bought direct from Dell (approx 19 months old) running Windows 7 x64 (original OEM with ongoing Windows Updates applied, inc Service Pack 1).

It keeps crashing with this error - about 4 times per week, without any apparent pattern - i.e. not when I'm doing anything on it. The machine runs a financial data feed (Morningstar Quotespeed) and pretty much nothing else, but it's on 24/5 during the week. Often it will crash in the middle of the night.

Core i5, 2.67 Ghz
6gB RAM
ATI Radeon 4350
TechniSat SkyStar 2 TV satellite receiver PCI card installed

Attached files as per instructions.

I have reformatted the HDD and reinstalled the OS from scratch, updated it from Windows Update and installed everything needed from scratch, with basic drivers (no fancy accompanying management programs - I was warned off ATI's software), and still this problem exists as before.

Any help would be gratefully received.