I have never came across this problem before, are you sure that you aren't using any other extensions or anything that isn't compatible with StuffPlug very well?
Try the following, uninstall MSN Messenger, Messenger Plus! 3 & Stuffplug, then go to C:/Program Files/ and delete the folders "MSN Messenger", "Stuffplug" & "Messenger Plus! 3". Then reboot your computer, then download from the following websites:
http://messenger.msn.com/
http://www.msgplus.net/download.php
http://www.stuffplug.com/
And download the latest versions, be aware though, that MSN Messenger 7.5 is not 100% compatible with Messenger Plus! & Stuffplug, it is only 95% compatible.
