Your stand-alone Autodesk product licenses have become corrupted and you want to know how they can be reset.

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 Settings\All Users\Application Data\FLEXnet\

Vista/Windows 7

C:\ProgramData\FLEXnet\

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.

Original post: http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=15890817&linkID=9240617&CMP=OTC-RSSSUP01