If it's a retail motherboard it may have some "performance" features such as overclocking and/or memory voltage modification.

Check to see if everything is on Automatic settings in the BIOS or if for example the voltage of the RAM is adjusted.
I recall once reading a motherboard review where they attributed the slightly higher performance of the board to the fact that the front side bus speed was ever so slightly elevated by default (think from 133 to 135 MHz or something like that). Something like that is within tolerances for most quality RAM anyway, but just in case there is a manual setting for voltage in there make sure it's not terribly over or under what the modules need. Having the wrong voltage will kill hardware a lot faster than a 1-2 MHz overclock.

The a7v600 is one of the worst KT600 implementations I've ever come across. It's fussy about everything, from what memory it will run to what expansion cards you put in it, and what PSU you use to run the system. Even worse, the things have a tendency to pop MOSFETs (generally the one near the RAM slots) or fry whole power traces from the ATX connector all the way to the FET it leads to. I have FIVE dead a7v600 boards, 3 of which are charred. One is mine, the others were taken out of machines that came in for repair (back in the day). No, really, even the ECS KT600-A is better than the A7V600, and that's saying a lot.

What I think happened here is Asus didn't give a crap about this relatively low end board (if I remember correctly the KT600 was launched at the same time as the KT880 and after the nForce 2 chipset) choosing to focus on other models like the excellent A7V880.

Unfortunately I can give no constructive advice... try sourcing a set of PQI or Kingston memory modules. Crucial, Corsair, Geil and other performance brands are unlikely to run well on the thing.

Never had a problem with these boards, but i DID use kingston ram with them. So yes, try that.

Given that this board is not a modern MB this thread should have been in Marvin.

collector wrote:

Given that this board is not a modern MB this thread should have been in Marvin.

Moved.

I had a main system running on A7V600 for years and no problems at all. It has moved now to the archives, but I am sure if I power it on again it will still run.

Something must be degrading. Could just be a bad RAM module but I think a motherboard or PSU issue is more likely. Check whether your voltages are still good, preferably with a multimeter. The BIOS health monitor is sometimes inaccurate but it's better than nothing.
I don't know what capacitors that board used, but look at those also.
Maybe there's MOSFETs or other components on this board that run too hot and degrade with age - but that's just a guess, I have no idea about this board.

Have you tried swapping the memory modules? Is that one particular module always failing, or does the board just not like having both at the same time? Have you tried the bad module in another motherboard?

Oh yeah, the above replies pointed out a very likely culprit also: a poor quality power supply. Watch out for cheap brands riding on the fame of more esteemed ones such as Q-tec (passing off as Q-Technology) etc.