Do you have the latest dot releases for all the extensions?
WebAssist did make some changes to several extensions recently to improve issues with installing on Macs.
I have been able to install all of the extensions on Snow Leopard with no problem at all. A lot of the issues is because of the cache file that Adobe uses. See this to remove it: 146/
The Adobe suite is compatible with Snow Leopard or 10.6 - it just doesn't maximize the full potential of the OS as the apps were 32 bit Carbon based whereas the new CS5 will be 64 bit Cocoa-based... but they are compatible. I can assure that I have the entire Adobe suite working fine on 10.6.