Fedora :: Compiz Slows Down After RAM Memory Upgrade

I've just added an extra 1GB of RAM memory to my laptop (HP 530). Now I have 2 GB. Everything runs great, except Compiz and 3D games. It looks like anything that's related to the graphics card now slows down. Rotating the cube lags badly, so does the Burn effect, and UrbanTerror is lagging too.

Before the upgrade, I had a Samsung 1GB SO-DIMM, 667 MHz. Then, I bought a Kingston 1GB SO-DIMM, 667 MHz too. When the laptop boots with either of the SO-DIMMs (only ONE GB at a time), everything runs smoothly, like before. But when I put both of them (regardless of the order in the sockets), my video card seems to slow down at nearly half of it's speed.

I haven't tried with Windows yet. Also, my graphics card has a dedicated memory of 256 MB, so there's no memory sharing between video and the RAM.

I just don't get it. Also, there are other people that seem to have slowdowns after upgrading the RAM, but usually the whole system is affected. For me, it's just the video. It actually boots faster with the 2 GB. Yet I found no clear solution to this.

Running Fedora 10 i686, on a 32-bit Intel Core Duo @2200 MHz, video card Intel 945GM Express, with 256 MB of dedicated memory. The swap partition is 2.8 GB in size.