Early reports are that The King of Fighters XII is suffering from online play issues such as lag. According to a spokesperson for the game:
"While not all players experienced these issues, an update for the game will be available tomorrow, Tuesday, July 28th for the PlayStation 3 which should help improve the overall quality and stability of online play for everyone."
KOF XII is a multi-platform fighter, and the Xbox 360 version is getting a patch — that patch, however, has not been dated yet. It should be announced shortly.
Kotaku AU Note: Hopefully it'll all be sorted in time for the local release on August 27.