When FTM works from another User Account that usually means that something in your user profile has gotten corrupted, and it strongly suggests that the problem isn't with the program itself.
One place where user-specific files are stored is here:
Change Marco obviously to your username for Windows. This is the place that stores the sync files.
There is also this location:
Searching the registry editor for "Ancestry" and "Family Tree Maker" or variants thereof will probably reveal more places where files are located. It could also be that something in the registry for your user profile has been corrupted.
Sorry I can't be more specific, but I haven't had any errors yet of the kind you're experience, so I haven't had to dig around searching for ways to fix it.