Here is a picture of kingston memory modules I have tried.

Try to set it to DDR333 T2.

If it would work at 333Mhz, would the reason for it not working at 400Mhz be because of the motherboard or the low quality of memory modules? Basically I am asking if getting better ram modules would help or is this limitation of the motherboard and memory controller?

Your previous post says it came with PC3200 from Apacer.. are they DS or SS sticks?.. anyway...were those sticks running at full speed? if yes, then the new sticks could be the problem, if no.. maybe the mobo is the problem.

Have you checked bios versions for A8V?

No, that's related only to the memory controller in CPU. Never tried elpida modules with Athlon64 though, perhaps they need some timing tweak in other area.

It is the newest bios version you can get from asus site. All those kingston memory modules and apacer ones are DS. I have 2 identical apacer modules there and they work fine at 400mhz, T1 and 2.5-3-3-8 timings.
Here is a picture of one of them:

I can't think of any other reason for all the kingston 1Gb modules giving similar errors in memtest86 except either those kingston modules are bad quality or the motherboard doesn't like 1Gb modules dual channel.
I doubt all those kingston modules are faulty but I don't have another pc where I can test them. That is the main thing I would like to find out if I should try to find better quality ddr ram on ebay or if the problem is with the motherboard and it would not help.

Try to find 1gb Samsung UCCC modules in your local area.

I was thinking that if getting better ram modules would help with the problem and I am going to have to spend money on ram, I might as well go to faster ram like trying to find fast g.skill, ocz or crucial PC4000 ram. Then money would be going to a ram speed upgrade as well in addition of increasing amount of ram.

I had a similar problem. I installed 3 512Mb modules (Corsair Value Select) instead my 2*512 DDR 433 Kingmax. When i started MemTest i always got error approximately on 1392Mb. If i tested just 1 module everything was fine even with short timings. Then i changed settings in BIOS for memory in "Auto". I installed program nTune and i was surprised - nTune showed 333MHz for memory bus instead 400MHz. And when i started MemTest it showed 321MHz. All errors disappeared. For some reason bios changed settings with 3 modules.

All Athlon64 CPUs can't do 1T Command Rate with 2 dual rank modules in one memory channel and at the top speed.