Hi mekugi,
This problem seems to be not completely recognized yet as to why it happens. I would recommend you to read the following threads.
Black contact window
and
Blank screen after installing messenger plus 5.0
If none of the solutions discussed help, I'm afraid you'll have to either try to find a solution yourself or un-install Messenger Plus! for now and wait for an update which hopefully also fixes this problem.
In the meantime, keep checking the forums too of course.