I am not the brightest star at this sort of thing, but did three things that have made a real difference. First I cleaned my mac of everything to do with CS2 & CS3 (everything) and the ran as many cleaning, tidying and correcting progs that I could so that the HD was as pristeen as it could be.
Secondly I installed 4gig of ram (total 8gig) and set ram usage to 100% because as I dont run massive files 100mb upward I could afford to have as large a 'tile' size that I could get. finally there is a little prog on Adobe site that frees up how the ram/scratch disc works (dont ask me to explain), this also needs excess ram. Like I said no PS master class here. However if you go to the Adobe site and look forRam/Scratch disc and Tile size options you should find a more (no an actual explanation). Start with a CLEAN disc and install though, tiresome but necessary. Hope this doesn't dissapoint too much. Sorry I forgot that the download freeing ram etc from Adobe is primarily to prevent highspeed brush use from freezing. Knock on effect is to speed up ram use.