Firefox Error

So Firefox was having problems on a recent install, giving me a pretty nasty error message (below). Turns out it was a permissions issue that happens when copying from read-only media (like a USB drive with write-protect enabled). This sometimes makes Windows think the data is also read-only. Follow the instructions on this page next to "File permissions," but also check to make sure your drive isn't full.

"Could not initialize the application's security component. The most likely cause is problems with files in your application's profile directory. Please check that this directory has no read/write restrictions and your hard disk is not full or close to full. It is recommended that you exit the application and fix the problem. If you continue to use this session, you might see incorrect application behaviour when accessing security features."