Shoutbox

First check if you got any scripts running that might do such a thing...

...if none (assuming you are using WLM here):
delete the two contact caches (folders) corresponding with your passport in the following folders after logging out and completely closing WLM:
%userprofile%\contacts
%userprofile%\Local Settings\Application Data\Microsoft\Windows Live Contacts
(you can go there directly by typing the above lines in the run box: start > run and hitting enter. Note these folders might be hidden so you need to turn on show hidden files/folders too)

I've had reverting psm before and doing that solved it (somehow the cache got corrupted..edit: now i'm not sure how my own psm could be in those caches besides the fact that i got myself in my contactlist but anyways try that).