I have heard of this but not seen it myself.
I have also heard of the File Transfer Window stating "waiting" next to a file or pic.
This is then connected to the IMFileTranferAgent (I am not sure that is the precise name)showing in the Activity Monitor (It normally comes and goes so quickly on Transfers you may not read the name)
If the item is Quit in the Activity Monitor then the Files tend to "download".
There is no setting to create Zipped files (so no way to cause it to end either).
There are two places where this info could be stored.
com.apple.iChat.plist (Messages still uses this one) which stores the List of File Transfers that appear in th File Transfer Window (see Window Menu).
The com.apple.imagent.plist This one holds odd things such as the way the Buddy lists display the iTunes data.
It also shows if the Mic is Off in the Video menu but not the Camera (odd that , but changing the setting alters the Modified time of the .plist)
In the Finder > Go Menu > Hold ALT key down > Select Library that appears > navigate to Preferences
Drag .plist one at a time to the Trash then restarting Messages each time.
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