video fault requires re-boot

I don't know how to report the most common problem I have with Firefox.
Web site embedded video will cause the browser to hang. I try to force quit and the window closes. However, Ubuntu or Firefox thinks Firefox is still running, and I can't re-start Firefox. I have to re-boot to start Firefox. Major TV networks sites like NBC do this. Nice sites like YouTube and New York Times never do this.

When firefox completely crashes, a bug report to launchpad is automatically generated.
There is something in Ubuntu called apport, which generates crash reports for Launchpad.
When the program just hangs up, or when I force quit, no report is generated. Is there another way to force Firefox to quit? How should I collect data to report the problem? Who should I report the problem to?

Thanks.