Try what Chris4 said, but also try cleaning all your settings. So:
Uninstall Messenger Plus! Live.
Uninstall Windows Live Messenger.
Restart your computer.
Make sure C:\Program Files\MSN Messenger
and C:\Program Files\Messenger Plus! Live
folders are deleted.
Go to Start > Run, type "%appdata%\Microsoft" and click OK. Rename the "MSN Messenger" folder there (your emoticons, DPs, etc. are here with changed file extensions).
Go to Start > Run, type "regedit" and click OK. Look for the following keys and delete them (you might want to export them first):
Always be very careful when editing the registry, make sure you only delete those keys.
Reinstall Windows Live Messenger and Messenger Plus! Live, making sure you install the latest versions:
Windows Live Messenger 8.0.0792.00
Messenger Plus! Live 220.127.116.11
If it doesn't work, try restarting your PC again.
If it still doesn't work, you can restore your settings by importing the saved registry files and renaming the "MSN Messenger" folder in %appdata%\Microsoft back to its original name.