Ubisoft today confirmed on their community forums that a patch to fix the Private First Class achievement in Rainbow Six: Vegas 2 is in development. The achievement doesn’t unlock because players who have a Rainbow Six: Vegas (One) save file, receive a bonus which takes the total XP to a rank above Private First Class.
Ubisoft also said they are looking into reported online issues but those issues seem to be more PlayStation 3 based. No specific release date for the patch was announced but Ubisoft have said that "the connection issues have not been known for as long and will require more indepth research to establish what the issue is". Stay tuned to Console Monster for the latest on the Rainbow Six: Vegas 2 patch.