Shoutbox

Do you have any other add-on or plugin?

You could try this:
Close Messenger.
Go to the Start menu > Run, write "regedit" and press Enter.
Locate in the tree the following folder: HKEY_CURRENT_USER\Software\Patchou\MsgPlus2\<your e-mail>\Preferences
(where <your e-mail> obviously is your account's e-mail address).
Once you selected Preferences from the tree, a bunch of options should appear on the right, search for the following options:
PersoAwayRestoreAway
PersoAwayRestoreOriginal

If they exist, delete them (right click them > Delete).
Restart Messenger and check.

Important note:
What I described above is editing the registry. The registry is very important for Windows to be able to start and work correctly, so you should be always be very careful. If you follow my instructions exactly then there should be no problems.