Shoutbox

The messenger icon is replaced by another usually when WLM is locked, webcam or not. If you mean you can't find it, search the forum for "messenger lock" and it will give you some threads that may be worth reading.

If you mean the icon completley dissapears (not substituted for another) then it may be something to do with your webcam like you suggested, although it is unlikely. Can you post your webcam details if the problem isn't solved by the first part of this post