My version crashes and will not save games reliably, is there a patch to fix this?

I bought a digital download version from Direct2Drive. It ran fine for a few days, now it freezes, crashes and will not reliably save games. It also has slowed the loading of saved games and new levels etc to a crawl. Is there a patch to correct this problem? I have tried uninstalling and re-installing several time to no avail, the same problems show up again. When I tried to download patch 1.18 English I get a message that the game is not installed or is missing something and I need to re-install.