hmm okz.. if i remember 7.5 did freeze a lot on people ..i'd try this instead of repairing just uninstall Messenger an reboot the system an then reinstall messenger
ok press Ctrl+Alt+Del Then Go to Processes & search for msnmsngr.exe in the list shown and then right click End process easy! then open MSN 7.5 again & I hope everything goes ok.
Bye