This has already been written under the previous system used here at Apple Discussions/Apple Support Communities.
At that time all were held in a Central Library and later individual ones were placed in certain Communities (in some cases linked across several if they applied.)
Reinstalling in Lion (iChat 6) and Mountain Lion (Messages so called Version 7.x) is done by the Restore/Recovery process that reinstalls the whole OS.
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