If you haven't already, could you try disabling Firefox from using hardware acceleration? This is the usual workaround for incompatibility with your graphics card driver software.

"3-bar" menu button (or Tools menu) > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

This takes effect the next time you exit Firefox and start it up again. Any difference?

If this problem seems to be associated with Flash media, there is a separate setting for that. More information in this support article from Adobe: http://helpx.adobe.com/flash-player/kb/video-playback-issues.html#main_Solve_video_playback_issues

Thank you very much. Disabling hardware acceleration seems to have fix it. I had no crashes and display driver stops for over 5 hours.

I admit, I had heard earlier about this option, but had no luck earlier with a similar laptop (Asus N61JQ and ATI graphics) one year and it was solved only after a clean reinstall of Windows7. So I applied your suggestion without any real expectations :) Before, disabling all extensions helped but the extensions are most of the whistle and bells for which I prefer Firefox over IE and Chrome for a decade.