CMOS checksum bad... clear the cmos... should be a jumper on your board, and redo all settings in the bios.. RTM..  and how is you PSU holding up?

Took out the 2x1gb, and after double reboot no more CMOS and the graphics card registers again! I think 4 gb of RAM should be sufficient for now, so I will stick with that.

Edit:

Or not. It seems to do it whenever it cold boots. A reboot after it was already on seems to be what causes it to work properly. I just turned on the fast boot option, which if I am lucky will mean it goes through the warm boot process even when it is cold booting... Will post in a few mins when I cold boot it back up.

Edit 2:

Still no luck.

@pettson: Dunno how to change voltages on this mobo. The manual is of no use, and itself has enough typoes to suggest they had it written by an illegal immigrant who only speaks spanish and then was edited by a Chinese worker on their assembly line who only speaks Chinese. They have a software app specifically for OCing and such, but can't seem to find a version for vista (xp and below it seems). My PSU should be more than adequate; its an 850W with plenty of juice. Also, checking my previous memory (2x1g) it was the same voltage as my new memory, and I had no problems with the old ones working. 

Edit3:

And now it cold booted w/o giving my the CMOS. Methinks this is the definition of insanity... Doing the same thing over and over but expecting different results. Or in this case getting different results.

Can’t run that.

RTFM again.....pictures et al.

Unplug and push Power button. Clear CMOS (short JBAT next to reset button). Boot to bios and set 'Optimized Defaults'. Save, exit, boot back into bios and set correct settings.

Bios settings (5-5-5-15-2T) at 2.1V. 1066 Spd. AMD only supports 2 slots at ram rated 1066 / 4 slots at 800.

If you're still having problems, flash to 1.7 bios.

...Dickhead.

I wouldn't. Take it to 2 x 2 and run at 1066. 

That's what ya get for living on an island......160 in the Colonies......

Sounds like you overwrite part of the graphics cards memory when using more than 3GB. What motherboard do you use?

Some motherboards have a setting in the BIOS for memory remapping, you may need to activate that if available. Also, make sure you have the latest bios version.

EDIT: Apparently it's called "memory hole" on some bioses.

Memory mapping is the likely candidate. I've seen this many times when upgrading memory. Might be a BIOS setting to tell the system how much memory the card has, might be telling it where to map the video memory.

If it were power, you should be able to set all youtr memory BIOS controls to AUTO. that usually gets rid of any customsettings that might have been a problem. If you are alreadya t AUTO then BIOS wouldn't likely be the problem. But I have seen where more memory can be enough to cause an under powered system to stop working. More power supply would then ne the answer. Thermaltake.com has a powersupply calculator where you define what you have and it tells you rather accurately how much power you are using/needing. Check it out.

http://www.thermaltake.outervision.com/

As said already, many BIOSes (those without EPP detection and automatic configuration via EPP settings - most motherboards don't use EPP config by default, as not all memory modules use the technology) don't set the Voltage correctly, and when you got a memory module rated for 2.0V (as the XMS2 modules should be rated at) or 2.1V (which the Dominator modules should be rated at) running at 1.8V you're bound to run into problems sooner or later. When pushing the computer hard and you're memory is 0.2-0.3 below it's specified rating there's a high probability of instability.

Memory Voltage settings in BIOS often goes under "Overclocking" settings, or "Performance" settings. I'd strongly recommend you check this, as especially when using more memory modules running them below their specified Voltage can be problematic. (This can't really be understated, so that'd be the third time I mention that by now ^^)

Also, running a system with a full setup of memory modules, especially ones that require some more oomph (2.0V+) can be problematic, no matter if you got everything setup correctly. Many motherboards have problems handling it due to power distribution issues and such. I'd never recommend filling all memory slots with performance memory modules, as the M/B most likely wont be able to handle that. (I've had countless support issues with this in my work, so this is a relatively common occurance.)