Weird problems in game (6800nu 128mb)

[Vegeta]

Hi i get this weird when running games and 3dmark's.
When I play games or run 3dmark06 it runs well then suddenly it might go into an area of high detail - then my computer will just completly slowdown and do less than 1 fps.
An example of this can be in games like BF2/F.E.A.R/HL2 - when I run at high settings i do actually get decent fps on my Leadtek 6800nu but suddenly if I look somewhere that has detail it will completly slowdown to less than 1FPS - so I have to look at the floor to get the normal FPS back.
People with my card are getting around 2K in 3dmark 06 - I feel i can get this score also - when i start it battle of proxcon gets around 20-7 fps then from out of nowhere it drops to 0fps, same with the firely tests and the others.
What can be causing this problem? im running 700mb ram - is it purely due to that?

 

[Vegeta]

Ye I can understand why it happens in some games, but 3dmark06? I've seen people with similar specs score 2000 odd and im scoring 800 - well I've got 512mb arriving soon to add to this 512 - and will sell the 256 hope it helps.

 

[Vegeta]

Any other reasons why I may be suffering this problem guys?

 

[Vegeta]

Well my monitor resolution is 1680X1050 - but even games when I run at low resoltions this can happen, it's an annoying problem because I know my card can generate the frames its trying to show - but its like soemthings blocking it almost.