I'm thinking the same way, Falloutfan, but recently it's occured to me that if the save is looking for missing DLC that a patch might fix it by telling the game those items do indeed exist. We shall see.
As for the OP, do yourself a favor and turn off auto-save. It's the culprit of many, many, many game killing bugs.
Welcome to the save corruption club.I managed to dig my way out of it.And now save every 15 minutes.And after I save,I load the save to check it isn't corrupted. I was at 53 hours when the save bug hit me.
The problem is, it does not seem to be one set of circumstances that sets it off. I wish I knew about the problem beforehand before walking blindly into it.If I did not dig my way out of the mess.I'd still be pretty angry.
Two types of save corruption,the no dlc message that takes you back to the start menu,and the loading screen freeze.