Hmm, odd!
Also check the 'Mem Usage' column (after pressing Ctrl-Alt-Delete). I'd expect your browser to using (perhaps) 150,000K. (If the figure is massively higher, your browser is hogging memory). Nothing else should be much above, perhaps, 20,000K.
NB: I'm assuming that you're currently experiencing problems with using your browser efficiently (e.g. by getting normal speed scrolling). If the problem is intermittent, the Ctrl-Alt-Delete checks will only show the cause of the problem while it's actually occurring.
Chris