First off here is the computer specs.

General:
Processor: Intel Pentium 4 Prescott CPU 3.20 overclocked to 3.47
L2 cashe: 1024KB
Memory: 1024MB (60% used)
Mainboard: ECS 915P-A2

Graphics:
Monitor: Samsung SyncMaster 2033SW/2033SWPLUS
Video Card: NVIDIA GeForce 8500 GT 1GB (overclocked)
Mode: 1600x900 with 32 bit color

Windows: Windows Vista Home Premuim (6.0.6001)
SP1

Background programs:
AVG
ZoneAlarm
CounterSpy
Windows Sidebar
RealTek AC97 audio

Now the problem is when im online after about 30 or so min my internet locks and firefox will not shut down in my tasklist, and sometime IE still works but not always when this happens. To reboot i have to hold the power button to turn off because restart on windows menu fails to turn the computer off.
Any ideas? Im exhausted on this problem.

Computers & Internet - Mozilla - Firefox