If you have updated Ubuntu 8.10 recently, and after the completion of update, when you try to start firefox you would probably end up getting the following error message "Could not find compatible GRE between version 1.9b3 and 1.9b3". This is a small bug with the recent firefox updates. But there is an easy work around. Take a look.

• Open terminal.

                        Applications -> Accessories -> Terminal

• Simply type the following in the Terminal window

                         sudo xulrunner-1.9 --register-global

• Now try starting Firefox. And it should work fine. Let us know if there are any issues. :-)