Thanks again for all the advice, guys.
A brief update: I have been working in CS2 today, monitoring memory usage, changing the settings that MrTom suggested - no joy. It's still glitching, and apparently getting randomly worse or better without much input from me at all!
Memory usage is not causing me any concern - it was set at 55% default, and didn't use that much (at maximum, opening a large file, it got to about 1200mb - just under the 1500mb that's available on that setting). I changed it to 70% (1950mb ish) just to test, and that had no effect on the problem.
I didn't see the 'creeping' memory usage issue really occurring either, it was quite stable. But I unticked the font display setting all the same - no effect.
The only remaining culprits to test are the graphics tablet or the lack of Flash - both of which I will try to play with later this week, as I've now run out of afternoon. 
Still, I got some painting done, which is always good.
All in all, if there does turn out to be a fix for this, then that's fantastic. But at the moment, I'm finding I can cope with it as a minor annoyance. My only concern is the effect this might be having on the stability of my system as a whole, with continued use...
