I have searched around a bit and found out that this (or very similar) is quite common problem. It was reported that people get data corruption while using nForce 4 based system regardless the OS. http://www.nforcershq.com/forum/1-vt5108.htm
- here is a huge thread about that. It seams that this behaviour is caused by hardware not by software. Although people write about problem disappearing after BIOS update, it haven't helped me. Now I have noticed that both NVIDIA GeForce 6150 GPU (with a radiator) and NVIDIA nForce 430 MCP (a bare chip) get that hot during operation that isn't possible to keep a finger on them. Is there a possibility that the heat causes my problems?