are they installed in default directories? or did u choose where to install it? it may be that but it may not... i found that the what im listening to feature didnt work because i had msn installed in a diferent folder....
what about if you manually run the stuffplug exe? anything happen then?
Does it say "not loaded" in Plus! - Preferences - Plugins? if it does, then please take a look at this thread on the Stuffplug forums: Stuffplug: Not Loaded