Abit KT7A: System lockup after stopping stress test program, why??

[legendma]

Anyone know why my system locks up when I close the program which stress tests my system? I mean during the stress test, the system is under 100% use but doesn't lock up at all. Once I tell the program to stop, the system locks up. Anyone know why? I can open programs, and do other stuff but immediately halting a stress test, and lockup. Here's my specs:

Abit KT7A w/ ZT Bios
AXIA 1Ghz OC to 1.4GHz (10x140)
ThermalRight SK-6 Heatsink w/Delta 38cfm
Adaptec 29160
2 - Quantum Atlas 10k 18.2GB U160
2 - 256MB Corsair Cas2 PC133
SB Live Value
Adaptec 10/100 NIC
Windows 2000 Professional