Does the browser lock up when you start it, or when you are using it?

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

It starts fine and locks up while using.

clbish said

It starts fine and locks up while using.

That sounds like your FF Browser has gone bad or corrupted somehow causing software issues. What could be done is uninstall FF completely and deleting the Mozilla folder-but before this backup your bookmarks if any so you can import them back. And then reinstall FF from clean install and see if the problem doesn't persist.