Shoutbox

If that happens just with your account, then it probably is a setting as you said. Close Messenger and delete your account's settings this way:

Go to Start > Run, type "regedit" and press Enter.
Navigate to HKEY_CURRENT_USER\Software\Patchou\MsgPlus2.
Right click your e-mail address and click Export, then save your settings somewhere.
Right click your e-mail address again and click Delete. This will delete your account's settings (in case you want them back, you can double click the file you exported previously and they will be restored).
Open Messenger, log in and see what happens.

WARNING: You should be careful when editing the registry, as it contains important data for Windows and all your programs, if you carefully follow the steps I described, then there should be no problems