I hadn't played SWBF2 much in the last few months, but I started playing it for a while yesterday, and it kept getting choppy and slowing down.
Eventually the CPU usage went from about 45% at start to the 87% and then into the 90's %'s after a few minutes of playing, (1 hour or more). I have a Phenom IIX6 1090T, and GTX260, which has always been plenty powerful enough. I checked the CPU temps, reinstalled windows, and same thing.
So then I rebooted to a 2nd (old install from 18 months ago) of Windows XP on another drive, and SWBF played just fine, CPU usage at about 24% jumping to 29% sometimes. Perfect play. So I figured it must be a windows xp update or AVG causing the problem.
So on the original drive and new brand new install of XP, I uninstalled AVG, and now it works perfect. No choppyness, and CPU usage in the 25% range. So now I just need to find a new antivirus.
Just wanted to post this here, in case anybody else starts having issues, because AVG is a widely used antivirus. They recently put in some CPU-usage-monitor, which seems to be the culprit that is eating up the CPU in game!