It's not just that patch of ground you're getting stuck on, there's a big invisible block that you just can't enter. I'm not sure exactly how far it goes.

I hope you still have a save from the previous level, because as far as I know you can't fix this bug if it's already happened, you can only avoid it. If you've saved with the bug in effect, the only thing you can do is noclip through the invisible block area. Open the console with the ~ key and type "noclip" (without the quotes) to toggle clipping.

If you do have a save from the previous level, then try running the game in Windows 95 compatibility mode before returning to this level. This bug is also very common in the very beginning of the first level of Wages of Sin, but in Win 95 compatibility I hardly ever have it happen there, so it should probably stop it from happening here either.