What have you tried so far to sort this ?
I would restart the computer as a first step.
You may need to use the Activity Monitor (Applications/Utilities) to find and Quit the imagent item (it will be in lower case).
Any other history around this issue and/or error messages that have been seen would be useful.
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously