New Home Theater PC restarts when recording live TV in Vista MC

I built a home theater pc recently with the following specs:

MOBO: GIGABYTE GA-MA78GPM-DS2H AM2+/AM2 AMD 780G HDMI Micro ATX AMD Motherboard
CPU:AMD Athlon X2 4850e 2.5GHz 2 x 512KB L2 Cache Socket AM2 45W Dual-Core Processor
HDD: Western Digital Caviar GP WD7500AACS 750GB 5400 to 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive
Memory: Kingston 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory
Case/PSU: Antec Minuet350 Piano Black Steel MicroATX Slim Case Computer Case 350W 80PLUS Certified Power Supply
TV Tuner: Hauppauge WinTV-HVR-2250 Dual TV Tuner / Encoder 1229 PCI-Express x1 Interface


I installed Windows Vista Home Premium just fine and have been playing around with Media Center. Whenever I view live TV in Media Center, the hard drive churns a lot and I can see via performance monitor lots of write activity (since Media Center is acting as a DVR and essentially recording the video to disk), and within 1-10 minutes the system will reboot leaving no traces in the Event Logs. The only traces of the shutdown I have are messages in the Reliability Monitor under Miscellaneous Failures saying:
"Disruptive Shutdown, Version 6.0.6001 Service Pack 1, The computer was not shut down properly"

I have narrowed it down to this singular scenario which causes this to occur. I can watch TV through another program that isn't recording it and everything runs smoothly for long periods of time. I can watch locally saved video just fine also and CPU temps and usage is still really low. It just seems to occur when recording video (not even HD, just standard def) from the TV tuner. Otherwise the system has great up-time. When recording TV the cpu/nb/system temps are all <100 degrees F.

I'm having trouble narrowing down what is causing this issue. I've removed all other unnecessary components, but there's still the TV card, mobo, hard drive, power?, memory that could be culprits. I've run some memory tests and that doesn't seem to be the issue.

Any thoughts or suggestions where to go next?

Thanks!
Aaron