motherboard or ram faulty?

A while ago I built a system for my brother from spare parts and parts going cheap. At the core of the system is a DFI LanParty UT RDX200 CF-DR, an Athlon 64 3200, 1GB of Ballistix PC4000 DDR and a X800GT AIW.

He doesn't use the system for games and it has served him well until now. The previous load of Ballistix ram had been faulty and was replaced by crucial.

At the moment the system is very unstable and we are having trouble restoring an Acronis True Image file of the drive I created in January. It is failing memtest 86+ with both the Ballisitx ram and some Corsair Value Select stuff that was previously known to be working. It is getting a lot less errors with the Ballistix though (2 errors after 27 passes). In fact it often wont boot properly with the Corsair. I have had the Ballistix at the recommended 2.8v and the Corsair at stock and have not been fiddling with ram timings. I have done CMOS resets in between changes and I have flashed the BIOS to the last official release.

Am I unlucky with ram or is it likely to be the motherboard?

What kind of error are you getting in memtest, test 5? What core of processor are you using, ie. Venice core or is it older? Did you change anything before the error started or was it out of the blue?

My first two questions relate to having seen memory errors start on a Newcastle chip, it couldn't handle 2Gb of ram (754 chip) at DDR400.

The machine was starting to crash more and more often. Previously I had it set up stably. To be honest I can't remember which test it was that it failed on, I might have to rerun that test, I can leave it on tonight as my brother isn't home and report the results tomorrow.

It's a Venice E6 core chip. I have 2GB of ocz platinum rev2 in my own machine that I could try but i'm loath to remove just yet as it's buried under a xp120 heatsink.

With the Corsair ram it has been having problems booting and has been freezing in the BIOS most times. The ram was previously running fine in an A8N-SLI SE.

Motherboard is my guess. Check that the voltages it gives (well as you can with software) are what it says it gives. Sometimes the voltage regulation is faulty.

Thanks for the advice I'll run some tests in the next few days and decide whether to rma the board.