then try to compile the with the final name you're going to use
Also, do this: close messenger, unregister the dll (with regsvr32 /u dllname.dll), register it again and start messenger.
Ah, btw, and make sure plus loads the dll in your account (plus > preferences > plugins > you dll should be checked) Maybe your dll did something dodgy and the plus' protection removed it from the list of dlls to load.