First try uninstalling Messenger Plus! then downloading it again from
http://msgplus.net/download.php and reinstalling it.
If that doesn't solve the problem, try the following steps.
1. Uninstall MSN Messenger
2. Click Start> Run> type
%USERPROFILE%\Application Data\Microsoft\MSN Messenger\ Click OK
3. There will be some folders named by numbers. Find your ID using
http://www.m00.cx/misc/msgrid.php.
4. Delete the folder which corresponds to your ID. (This will delete your emoticons, backgrounds, winks etc. which you can backup with
MSN Backup
5. Download MSN Messenger from
http://messenger.msn.com and reinstall.
Hopefully this should solve the problem.