My husband and I have both had this problem on our PS3s along with another PS3 user from our FC. It is not the PS3 freezing, as the loading circle in the bottom right corner is still rotating and I can still bring up the XMB. It just stays in the zone title screen indefinitely. The only way I have gotten out of it is to bring up the XMB and quit game, which is a scary thing to do! ;.;