Your specs say Lion (OS X 10.7) and Messages is in Mountain Lion (OS X 10.8.x) (Although there was a beta during Lion's life time).
I would Repair Permissions (Disk Utility in Applications/Utilities)
I would also check the Font Setting in Messages Menu > Preferences > Messages.
It should list a Font your Have and that is Active in this OS boot.
The Default is for it to list Helvetica.
In previous versions if this font was absent or turned Off then the App (And others ) would not launch.
I have not purposely tied this in Mountain Lion.
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