One thing you could try is to "hide" your existing Family Maker Tree Folder in "My Documents". I usually rename with "hide" at the end, e.g. "Family Tree Makerhide". Then open up FTM2012 again. It should recreate the folder structure. If it does, copy the contents of the hidden folder back in the new folder and use FTM to open the .FTM file.
If you're lucky that will work. If not then there is probably something wrong with the .ftm data file.
The backup files, suffixed ".ftmb", are simple Zip files containing the media folder and the .ftm file. If necessary, they can be opened using e.g. 7zip (make a backup copy first) and the contents copied to the Family Tree Folder, overwriting the existing contents.
The .FTM file is an SQL format file and can be corrupted if something happens before the updates have been fully incorporated.