[mythtv-users] New system: hard freezes - looking for help !

[Warpme]

Hi *

I just finish build-up of my new shining HTPC system for living room.
Setup is:
ASUS P5P800-VM
GF5200
Celeron 326 (2,53G), 512M PC2100 RAM
2xWDC320JB
PVR250, WinTV-Nova
Lascala LC11B case.
R5D1 clean install

System looks really nice and I was finally happy to have really nice 
HTPC machine but....

STABILITY kills me :-(

System freezes hard in random manner.
After trying to find where is problem - it looks like use of on-board 
Eth port cause hangs (few Gigs traffic is usually enough to freeze).
I don't know - is it Eth related or simply Eth generating a lot of 
interrupts and by volume triggers other problem.

Initially I was thinking that it is heat related problem. In BIOS CPU 
has 50 C.
My GF5200 is really hot - but problem with overheating Video should 
manifest rather as artifacts - not whole system freezes.
Voltage in BIOS looks OK - so probably my PSU is OK.

Problem look challenging - so...

I'm asking You people for help !

Let use community knowledge,

1. What usually cause hard freeze (no any reaction to KB, mouse - only 
hard reset) ?. I always think that interrupt issues are main source.
2. I start to switch off in BIOS all possible peripherals: USB, 
Serials/LPT - still freezes (came to config with: HDD, Eth, Video and PVR)
3. I replace on-board Eth with PCI Intel LAN card - no change

What procedure are You suggesting for  nailing down this problem ?

Thanx in advance