If you go to Applications and click iChat once to highlight can you then do a Get Info ?
Apple/CMD ( or ⌘) and the i key together.
This will bring up the Info panel
Which version of iChat does it say it is ?
At OS X 10.7.3 it should be version 6.0.1
If this is OK then close the panel
Go to the Finder > Go Menu and hold th ALT key down - then Select Library from the list.
Open the Preferences folder.
Find com.apple.ichat.plist and com.apple.ichatAgent.plist plus th ones with AIM and Jabber in the File names.
Drag them all to the Trash
If iChat is NOT at version 6.0.1 then download and reinstall the COMBO version of the OS X 10.7.3 Update over what you have. (this should Update iChat)
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.3)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously