[xubuntu] Suddenly Can't log into AAdvantage account with Firefox

I suddenly can't log into my American Airlines Advantage frequent flier account from Linux. The login page just comes up blank. I can log into any other web site with no problem. I am ruing Xubuntu 14.04 and Firefox 46.0. I called American, but they were no help. I logged into my AAdvantage account with no problem from Firefox on a Samsung tablet ruing Android, so the account is fine. I just ran a complete update on xubuntu including updating firefox. I suspect that I might have a Preference set wrong or that I have an incompatible add-on or plugin. However, I have disabled all extensions, under Preferences>Content unchecked the box to block popups, under Preferences>Privacy set to always accept 3rd party cookies, under Preferences>Privacy Tracking I unset the Track box, under Preferences>Advanced>General I unset "wa me if web sites redirect or reload the page".

Anybody else having this problem????

Could it be something wrong with Iced Tea???

Any help is appreciated........