Odd issues with fps

Every now and then when i jump on DOD:S net graph will show 24fps and 111ping. i usually get around 120+ depending and ping around 80-90. It would seem that at times if i alt tab out then back in it fixes the issue. I had beta drivers but just reinstalled the standard drivers. I used Driver cleaner to clean etc. I have an 8800 320mb not overclocked and 4300 at 3.2. This has been running without issue for about 3 months now. This just started happening about 4 days ago and as far as i can tell my card is not overheating about 67 load. Sorry if this is the wrong place to post. Any ideas?

EDIT: I never got a chance to test other games due to a spyware issue. In short i reformatted my drive as it needed it any how. And what ever the conflict may have been has yet to rear it ugly head. SO it may have been infact a virus related issue.

Nothing is really coming to my mind, so I'd probably check your running processes when the slowdown occur. Its possible something is stealing a lot of CPU time and killing your performance and lagging your network. What can you think of that has changed since you started noticing the problem (new hardware, new software, updates, system settings changes, etc)?

JigPu

...could it be a virus?

Doesn't really sound like a video card problem if you fix it by alt-tabbing. Does it happen after a periodic time? ex. 1h into gaming or something? Does it happen with other games?

Both games are on steam so that could be part of it? Prior to this (the day before) both Hitman and DOD would lock-up my comp after about 15 min. Needing a restart to fix. I did run COD:2 and got the lock up after about 15min too. I backed off my OC and that seemed to help accept when i tried to run COD:2 again the next day it would just freeze up, not lock the system up tight just crash itself. I do believe i played Quake4 longer than the 15min time frame before changing anything. I have since clocked my chip back up and thats when i noticed the odd fps occurrences. I do have a few other games i will try out and see what happens.