I have the same board, also with a dual core Athlon...
I have encountered (but not overcome) just about every problem people are having with this board... this particular problem I was able to overcome by doing No. 4, below.
You mah want to first try the usual suspects, however. Each of the first three suggestions, below, are really just additional ways to attack one issue--
A Stupid BIOS on a not-so-stable MoBo.
All things being equal, I think ASUS's Auto-clocking features are the shiznit. As you are noticing, all things are not equal with our board. Simply put: relying on our BIOS to stablize our board is like paying the stupid kid at school to do your homework.
So, here are three ways to take the stupid kid out of the equation (but first read no. 4, below):
1. The latest BIOS has trouble holding our settings, and this is especially true on the first reboot after you make a change. For some megalomaniacal reason, on a cold/hard-boot, our BIOS will automatically set values that we've manually set. But as I mentioned, on the second reboot, manual settings should stick (unless you have No. 4 issue (see below)). So, forgive me if I am going too basic here, but without knowing your RAM specs, O/C, or BIOS settings, I am going to just throw everything at you... Start by loading your safe BIOS default settings and reboot a couple times (so the settings stick). THEN, re-establish your Overclock, then reboot *twice* (again, so the latest BIOS will hold your settings). If that doesn't work, and you've already looked at No. 4, below (hint hint), you can try the following to tame ASUS's Auto-clocking...
2. get rid of as many ASUS "auto" settings as possible, certainly for Vcore and Vdimm, if you know them. HT LINK SPEED too. This could be tricky if you're a beginner, especially when setting Voltages, so be careful. Also make sure VCORE OVER-VOLTAGE and COOL-n-QUIET are set to [Disable]. But wait, it gets worse, I'd also recommend taking some of the Auto settings away for the RAM, so
3. try setting both your RAM speed and the "top-four" latency settings manually, based on research you might find in fora specific to your RAM.
OR... and if you re-read Anandtech's article on our motherboard you'll better understand what I am about to say...
4. For some reason our board completely loses it when both (1) overclocking and (b) running the RAM at 1T, even if we only overclock just a tiny bit. For many of us, the constant BIOS resets were caused by trying to OC with our RAM set to 1T. If this is your problem, just enter the RAM configuration in the BIOS and set the
(i) ADVANCED-MEMORY CONFIGURATION-MEMORY TIMING CONFIGURATION-USER CONFIG MODE to [MANUAL], which should open a sub-menu, wherein you can then
(ii) change CMD-ADDR Timing Mode from [1T] to [2T]
I know, we must be the only people on this form who are unable to use 1T timings, but as the article points out, somehow the ASUS board makes up for this and we don't take the performance hit you'd expect when going from 1T to 2T.
Hope that made sense,