I open FF (happens in Safe mode too), and after a couple minutes of running it stops responding to input, but tabs on live websites continue to update content as expected. Then I use the task bar , right click and try to close, the confirmation box pops up but acts like it's stuck in the background, clicking on anything FF does nothing even though it's still running (usually). I've disabled all add-ons, and run in safe mode, same behavior. It acts like it's waiting for input from a process (thread) running in the background and I just can't get to it. Task Manager does not offer the option to bring each thread to the foreground to inspect. Patched to the latest version.

Any Ideas?