If your display picture keeps changing, you can repair this by removing all your display pictures manually. Go to the folder
C:\Documents and Settings\Username\Application Data\Microsoft\MSN Messenger\number, with Username being your Windows username and number the number that symbolises your email address.
Use
this little program to find out which number matches your email address. Go there and delete the folder called UserTile. Reboot and add your display pictures again; your problem should be fixed
Note: if you don't have that folder, try
C:\Windows\Application Data\Microsoft\MSN Messenger\number or
C:\Windows\Profiles\Username\Application Data\Microsoft\MSN Messenger\number instead.
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