Hi,
I am guessing Messages on the Mac has out or order iMessages in the conversations you are having.
Apple stated in the info about the OS X 10.8.4 update that one cause of this was fixed.
However it seems that there are many causes because people still report the issue.
For those other causes there seems to be no fix at present.
If this is not what you were asking try saying things another way.
If English is not your First Language try writting in that or use Google Translate.
7:32 PM Wednesday; June 19, 2013
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.4)
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