"Memory cannot bea read..." bla bla wtf?

I have problems with client crashing while gaming.I have got about 80 crash logs. While crashing i can see msg “memory cannot be read…” i have no idea whats going wrong. I have newest drivers i have tested my memory… everythning with my hardware is O.K.
Plese help me.

My comp specification:

Microsoft Windows XP Professional Service Pack 3 (DirectX 9.0c)
DualCore AMD Athlon 64 X2, 2600 MHz (13 x 200) 5000+
2048 MB (DDR2-667 DDR2 SDRAM)
ATI Radeon HD 4670 (512 MB) SyncMaster T220/T220G,SyncMaster Magic T220/T220G(Digital) [NoDB] (H9XQ609187)
Creative EMU10K1 SB Live! Audio Processor
SAMSUNG SP0842N (80 GB, 7200 RPM, Ultra-ATA/133)
Asus m3a motherboard