Quake 4 and RAM: Game occasionally Stutters.

Hello,

I recently rebuilt my PC. My vital specs are:
Core 2 Duo 6600 overclocked to 2.933.
Patriot DDR2 Dual Channel 800mhz 1Gig (2x512) 2.1v 4-4-4-12
EVGA 680i
8800GTX

My issue with Quake 4 is with the game set at Ultra Quality, when I'm playing in a level (SP), when I approach a door, the game will bog for a second or two, and then will continue to run buttery smooth.

This is the only game so far on my new rig that has exhibited this behavior.

Could this be because I have 1 gig of Ram? Should I add 2x1gig in the other dual channel sockets for a total of 3 Gigs?

Thanks for any advice.