I was afraid that was going to happen. It's not your video card, it's the fact that you're using mismatched sticks of RAM. There may be a way to resolve it, but I would prepare myself for the method to not be successful.
You have 2 kits of RAM that have different IC's (integrated circuits); they each like to run at their own specific timings. In order to overcome this, you're going to have to fiddle around and see if you can find a set of timings that they both can handle?
You're already familiar enough with the process by now, so tinkering should be easy enough. Open up cpuid again and on the memory tab list your timings. Btw, what voltage are you running at right now, is it still 2.0 volts?
Just know ahead of time, so you don't get discouraged or head off in the wrong direction trying to problem solve this, that it's most likely an issue you're not going to be able to fix as value RAM isn't known for its ability to play nice at settings outside its defaults. DDR2 is very cheap these days, and if worse comes to worse, you can get a 4GB kit for ~ $70.00.