You do-not need to reinstall.
And you can keep your savegame's.
If you have already reinstalled then...bummer
Go to Your M@B Directory , go to mods/native and make a backup(zip file) of the native folder. That will then go next to your native folder , with a name like Native.zip.
After that , go to your savegame's , do the exact same thing (make a backup zip file)
After that click here -
http://www.freewebs.com/wippersnipper/Native.zip
That is an original backup of the native folder (note: you need winzip , winrar , alzip or any other zipping program to use it)
Open the zip file after you download it. It should have all of the native folder's contents in it.
Ok now move the native.zip file to your M@B directory as a permanent back-up (make's it easyier for future use) , after that open the zip file , extract all the files to M@Bmodsnative folder. Overwrite the original file's.
That should fix the resting problem. If it doesn't work....well then reinstall
Does it happen to new game's? eg. if you click new game , then save it , then try an rest does it stuff up?