Copying large files >600mb causes kernel panic

[House]

specs:

Biostar 6100-M9
AMD Athlon 64 X2 4200+ 2.66ghz (OC'ed)
2GB PC3200 400mhz Dual Channel DDR/SDRAM
(2) WD SataII 250 GB (2) IDE WD 250GB (X2) Full Sata Support
Running Tubgirl 10.4.10 and Zephyroth 10.5.2
XFX Nvidia GeForce 7600 GT 256MB Full QE+CI Support both Tiger and Leopard

When ever I download or transfer files greater than 600mb or sometimes less i get a kernel panic

or sometimes when I watch a video. It's annoying what could be the problem

any help would be appreciated