So I'm at the end of the Dead City Streets map, I killed the slime mutant, and I walk up to the exit door, I enter... and the Dead City Central loading screen appears, only to throw me back to main menu after 5 seconds

I tried re-starting Steam/game, tried loading up from previous saved game, and it happens every time.

Anyone else have this problem? any suggestions? I've been looking for codes to skip to next map, but alas haven't found anything. Any help would be much appreciated. Thanx.

D.