I'm experiencing this in Firefox 38 (latest) on Fedora 22, and Firefox 3.6.24 (too old to expect support, but mentioning as another data point) on RHEL 6. I log in, and then get a blank white page. I can view source and see HTML, but none of it is being displayed (well maybe it's an empty white page, but that's not too useful =) ). "Safe mode" doesn't help, nor does Firefox's Safe Mode (disabling all extensions), nor does clearing cache and cookies. Chrome works fine on the same Fedora machine, and so did Firefox a week ago.