You might need to download your updates for your video card and whatever else. (I have found that a host of impossible and unsolvable problems have been solved merely by downloading an update.) If it's a runtime error happening to one save game, but not the others, then I don't know what to say, I'm in the same boat as you.
But if not, Another thing I learned is to bring up the task manager and start shutting down every process I don't need under my windows screen name, i.e. every single process except "explorer.exe" and taskmgr.exe because closing Explorer might shut down your computer, and the other is the task manager, and you don't want to close that until your done closing every other process you don't want running. I even randomly shut down some of the processes listed under "system" that I guessed I probably didn't need. I don't even know what half of those system processes that I shut down do, but I know that my game works without them so I shut them down everytime I play. But if you go doing that, be prepared if you shut down the wrong one because your computer might shut down and you'll have to reboot. I was lucky because I stuck to shutting down system processes that I didn't remember seeing when I first reset my system back to factory originals and ones with capitol letters since I didn't remember any capitol letters in any of my processes then either.
Another trick that I use everytime I play just about any game, and this works for just about any game giving problems with starting up or crashing or whatever. Click run, or in Vista, the little search bar in the start menu and type "Temp," without the quotations or the comma, of course. Then a temp file will come up. Delete all of those files in the temp folder. Then go back to run and type "%temp%," which will bring up another temp file in which you can delete everything. The files are okay to delete because they are just files that your computer stored there temporarily while it was using a program or running processes during boot up. And you will see, sometimes when you have certain processes running they'll have undeletable files in those temp folders, and they are undeletable because they are being used by the process. Thus I recommend you close out your processes before you delete the files in the two temp folders so that you can delete them all. Then empty your recycle bin. Another folder you can delete all of the files in C:\windows\prefetch, without the comma, of course. You can delete those files too because they are just files your computer writes whenever you open a program or process so that the next time your computer opens that program or process, it can more quickly access it and open it. I don't usually worry about the prefetch file because it has never seemed to make a difference concerning the stability of my game regardless of whether or not I deleted those files. The Temp files, however, made a noticeable difference, as in my game would only crash once every 3 to 4 hours give or take rather than every 30 minutes to an hour or so.
I don't think any of this will help you because it sounds like your problem is an acute consistent problem, as in it's a problem that has happened suddenly and has kept happening since the first time.
See if you can start a new game and then save it, and reload that new game. If it reloads just fine, then you know it's a problem specifically with the one saved game. In which case, you're probably in the same boat as me.
I just tried loading the game I was playing a couple of days ago and the application is termainated and CTD's. You can imagine how I feel about it - I was on day 2733 and was doing really well. 
