Try to restart the game. Log out of the server, press the PS-button and return to the Play Station menu. Then start the game agein, go directly to “create game”, press X when the “game options” are highlighted so that you can access the menu and move down to “ranked”. Press X again, than O and leave the other options. I suppose you don't really care what game you host. Then set “start” and let the PS3 rest.
P.S.: After 30 minutes (or the time you entered one game to last), the counter on your screen resets itself. This is no error and no reason to worry. After a bit more than 4 hours (I think the 30 seconds inbetween the games are not being counted) the trophy'll pop up.
At least that's how it worked for me…
