Shoutbox

Open up My Computer. Go to Tools > Folder Options > View tab > Select 'Show hidden files and folders'. Now go to your hard drive (usually C:\) then Documents and Settings, then your name, then the Contacts folder. You will see folders with emails of who have signed in on Messenger. Delete the folder with the email address your having problems with. This will delete your contacts cache, not your actual contacts. Once you've done this, restart Messenger and see if you still have the problem.