The TBC Cleanup Utility will scrub your Machine 100% for all TBC Related Files and the registry for all TBC Settings
Make sure that you backup any custom Menus, Import Formats, Project Templates, Options Settings etc in a Non TBC Related Folder on your PC so you can restore them quickly later in this process.
Use Control Panel to De - install TBC and I would also deinstall the following as well
- SCS Data Manager
- Office Synchronizer
- Feature Definition Manager
- Coordinate System Manager
Then you should run the TBC Clean Up Utility - You can download it from this Forum at this link
Click Here to Access TBC Cleanup Utility
Now you have scrubbed your machine - do a Clean Installation of TBC
Hopefully through this process you will fix your issue and Feature Definition Manager will run again
Alan