I posted a possible fix for this on Monday. First this is a known issue that apparently exists for all versions in single player mode. In many cases at location 50,50 on your map there will be a spawn pile and possibly other oddities (twisted walls floating in the air for example). If you do the following you should be able to save again:
Travel to location 50,50 and if there is a spawn pile there, make a note of the exact location and make at least 4 foundations
Run the DestroyWildDinos command from the console - this will get rid of the spawn pile, wild dinos will usually start respawning soon
Immediately lay down the 4 (or more) foundations at the noted location - this will prevent new spawn piles at that location
Follow your usual save process.
Good luck, and let us know if this worked for you.