Too much RAM causes lower framerates ?

Background information:

I have an Tbird 1.2ghz on an asus A7V133 (266fsb) and a geforce2 GTS 32megs.
The rest is rather inconsequential to my problem...

Problem :

I used to have 1 128meg Specdeck chip and 1 256meg Infineon chip (both 133mhz) in my system and had wonderful performance coupled with great framerates in most games (ie. counter-strike = around 175-250 fps)...

Since I installed an additional 256meg Infineon, everything has seemed to be slowed down : certain modules don't load properly (midi sets) and counterstrike yields 50-75 frames tops.

I removed the specdeck and left only the infineons and had the same problem, however, any combination of specdeck and infineon seems fine. I replaced BOTH infineon chips and the same results occur, so it is most likely NOT the RAM.

Solution :

Any ideas guys ????