Well, after a thorough search of this section I still cannot find such symptons with a solution that works.
I have the GOTY edition, and everything installs fine. The moment gameplay starts (or the map scrolls during the menu screen), the movement is plagued by a one-second jump every few seconds. I have read the thread which details how to remove this, but I have a Radeon 9800 Pro card - ATI, not Nvidia. I have fiddled around switching between resolutions, viewing distance and visual quality etc but the problem still persists.
It happens mainly during a game when I turn directions - a one second freeze, then smooth, then a freeze. Extremely annoying as I didn't experience this on my older computer which was about a third of the power!
My system specs are:
Athlon 64 3000+ Processor
1024MB RAM
Sapphire Radeon 9800 Pro Graphics Card
ABIT NF8 Series Motherboard
Fully-patched 1.96 GOTY
Thanks in advance to anybody who can help me resolve this.