Yeah, though I still wouldn't
I know it wouldn't really cause a problem though. I just think it sounds better if you have an even number hehe.
As for the RAM. This seems to be cropping up more and more with RAM modules failing and not working correctly. I thought RAM was actually usually rather stable.... Anyhow, yeah, do what Connchri says if you can.
If you can test a stick of RAM, this might be the best ticket.