Please use this site: http://bugs.adobe.com/jira/secure/Dashboard.jspa to report your other issues, also this issue. We will try to reproduce and investigate your unable to report a bug issue from flex builder. thanks.
Someone else who reported this error had a USB mass storage device attached to their system. They found that detaching the USB drive solved the problem (ie, made the error go away).
If you happen to have USB storage devices attached to your system, try removing them, restarting Flash Builder, and see if the problem reproduces.
Flash Builder QE
There's just a C:\ drive.
However, it's a laptop, and the entire C:\ drive from MBR to partition is encrypted with TrueCrypt to protect data in case the laptop is lost/stolen.
Is it possible that an encrypted disk confuses Flex licensing?