Did you try to disable all plugins?

• https://support.mozilla.com/kb/Troubleshooting+plugins

Did you submit any crash reports?

See:

• http://kb.mozillazine.org/Firefox_crashes
• https://support.mozilla.com/kb/Firefox+crashes

I'm sorry, I thought I was clear. I totally removed the firefox profile, including all extensions, plugins, personas, add-ons, etc. This happens with a completely empty .mozilla profile with nothing installed.

And I thought this was a crash report.

Plugins aren't disabled in Safe mode and are found via a scan, so you will still have all plugins if you create a new profile as you can see in Tools > Add-ons > Plugins

• https://support.mozilla.com/kb/Troubleshooting+plugins
• http://kb.mozillazine.org/Issues_related_to_plugins

Nope, All plugins disabled, restart in safe-mode, firefox crashes within 3 seconds of clicking on the bank website, and no crash report window popups.

OK, I've been playing with it all day. I can load the website if javascript is disabled, but Firefox immediately closes upon given permission to enable scripting. I am enclosing two pics, showing the page with firefox (javascript disabled) and Opera (javascript enabled). I'm guessing that this is a website or javascripting issue and not a firefox issue?

You can try to disable some of the JIT prefs (Filter: jit) on the about:config page to see if that helps.

• javascript.options.methodjit.chrome
• javascript.options.methodjit.content

• http://kb.mozillazine.org/about:config

Removed FF9.0, installed FF5.0, checked jit settings, reinstalled/removed FF9.0/5.0, set jit exactly same, no joy. I have installed Opera 11.6 (My wife uses the website for online banking), imported FF bookmarks, set it up to look like FF and she didn't notice the difference. I can use FF9.0 as is. Thanks for your help.