Go to C:\Users\"User Name"\Documents\My Games\FalloutNV\Saves
Here you will see your auto/quick saves and any hard saves. Now if your one of the lucky ones, you should see 2 auto-saves and 2 quick-saves. And THATS RIGHT! One of these is all your hard work. The ones ending in .bak are your correct ones. Simply rename it and delete the .bak. Feel free to delete the other 2 ones that have so frustratingly overwritten your hours of play, giving you a mini-heart attack. After deleting the .bak, you should discover your correct auto/quick saves in the load screen, safely able to continue playing from your original position.
Hope I got to people on time before they auto/quick saved again. Good Luck out there guys!
EDIT: I did put almost btw. About 10% of the time, the file was not actually saved. Sorry bout the guys who lost their work =/
Also, if you auto/quick saved again AFTER originally losing your auto/quick save, you have made a NEW original, and your .bak will be what you just auto/quick saved. So this is a rescue attempt at people who have yet to begin playing all over again, not those who tried again and ultimately wrote over their original progress.
EDIT: the only way to permanently delete your old saves is to permanently play in offline mode. At least till they patch it.
However, this only works with steam-bought digital downloads.
This may also be the reason why the .bak trick isnt working for everyone.
For those it has worked for, could you please state if you were using a steam digital download or a hardcopy?
FIX: With my suggestion, you MUST change the .bak file to .fos once the game is already started up. or you will just overwrite the file you just fixed. So simply alt-tab while the game is already up. I apoligize for this one mistake and hope it helps.
FIX: Now to stop this problem from happening ever again. A new fix then the original I had has now been posted. Ive tested it again, and for now it is a bit easier as well as safer for your system.
I, myself use this fix and its perfect. I dont take credit for it. lefty666 Is the first I saw post this as well as ElusiveByte adding a tep by step.
Here's an easier fix than the batch file. In the ...Steam/userdata.../22380 folder, delete the contents of the /remote folder, then turn off Write Access (for all users and administrators) for the /22380 folder in the Properties/Security tab. That way, no new autosaves or quicksaves get backed up there, and there is nothing for your saves to revert to.
Note: you might need administrator access to do this. If you are not an admin on your PC, ask someone who is to do this for you.
Step 1: Delete all fos and ini files in the remote folder. These are what it is using to copy over your newer saves. Delete them this one time and they will not come back after we change the permissions.
Step 2: Open the properties of the remote folder by clicking on it, then right clicking and choosing Properties.
http://i.imgur.com/TFfWr.jpg
Step 3: Click on the security tab. If you have Windows 7 (Or vista, I think) you will see an Edit button. Click it. On XP, you can just go to step 4.
http://i.imgur.com/IGPfk.jpg
Step 4: In the list of users and groups at the top, choose either your login name or the Users group. If you see neither, post a reply and someone can help you out. In the box at the bottom, check the checkbox under the deny column in the Write row. You may need to scroll down a little. It will warn you about using the Deny feature, just hit OK.
http://i.imgur.com/0ms41.jpg
Then hit OK on this and the first dialog box and you are all set. No either you or the whole Users group (depending on what you chose) cannot write to this folder.