It could be that the program is overwhelming your 32 bit system. (As I'm sure you know, a 32-bit operating system won't be able to access more than 4 gigs of RAM, so all of that extra RAM isn't giving you much more power.) This is further indicated by the fact that even FireFox browsing is affected.
What processor are you running? How much free, clean, freshly defragmented space is on your hard drive?