Issue
Your stand-alone Autodesk product licenses have become corrupted and you want to know how they can be reset.
Solution
Use the following steps to reset the stand-alone licenses for all Autodesk products (version 2010 or higher):
1. Make sure there is no Autodesk product currently running. If there is, close the application.
2. Rename the adskflex_00691b00_tsf.data file to adskflex_00691b00_tsf.data.old. This file can be found at the following locations:
Windows XP
C:Documents and SettingsAll UsersApplication DataFLEXnetVista/Windows 7C:ProgramDataFLEXnet
3. Restart your Autodesk product and go through the activation procedure again.
Note: This file contains all product activations for all 2010 and higher Autodesk products installed on your system. You will need to re-register these products if this file is renamed/deleted.
via
Autodesk – AutoCAD Services & Support – How to reset your stand-alone Autodesk product licenses