My new myth box has been in service for just over a month. It consists of:

AMD XP3200
Gigbyte Mobo w/VIA chipset
Nvidia FX5200 GFX Card
256MB Corsair Value Select

It started out behaving itself quite well, the GFX card had actually been in another machine which showed zero problems. Slowly it's been becoming less and less reliable but only when watching videos, it basically hard locks and only a reset will bring it back. As a recording backend, a transcoder and a web/mail/DNS server it performs flawlessly. If you don't watch video on it, it will run and run. I ran memtest for a couple of days which showed nothing. What do you guys think? Flakey gfx card, mobo chipset issue, overheating (there are two case fans in already)?