From the devs at Killzone.com
"Hi all,
Some of you may have experienced issues with the Visari Palace mission from the Killzone 2 campaign mode after installing patch 1.28. We've received reports of crashes, graphical glitches and general progression issues - particularly when playing from a save game created before patch 1.28. The problem will be fixed with patch 1.29, which is due for release on Thursday , July 23 at 9:00 AM GMT..."