I’m using CS3 on Win XP (32) and thought a couple of experiences might be useful here:
I had a recurring problem with crashing, especially with Encore. It turned out to be the /3GB switch I had added.
Twice in about a year a problem came up with a PP-exported frame: every time I wanted to save/import/export or even look into the folder containing the file, I had a crash. Using a DOS window to delete the offending file solved it.
Apart from that, it’s been reliable. We have FC Studio also, but I end up using CS3 more because of AE. Looking to go to CS4 on Vista.