It's worth deleting cache which may be corrupted...
quote:
C:\Users\your_username\AppData\Roaming\Microsoft\MSN Messenger\
C:\Users\your_username\AppData\Roaming\Microsoft\Windows Live Call\
C:\Users\your_username\AppData\Roaming\Microsoft\Windows Messenger\
C:\Users\your_username\AppData\Local\Microsoft\Windows Live Contacts\
C:\Users\your_username\AppData\Local\Microsoft\Messenger\
C:\Users\your_username\AppData\Local\Temp\MessengerCache\
C:\Users\your_username\Contacts\
Note: I suggest backing up before deleting (e.g. 3rd from bottom will delete custom smiley's, display pics, winks, scenes, etc.).
Source:
CookieRevised.
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