upgrade went smooth. firefox browser already open during upgrade - just did a shift+reload to get new UI. All was good. restarted browser and now I get a login screen but it just spins then comes up blank. This is both for Mac and windows. Safari and IE are fine. I can log into the admin console with FF and if I view email from an account there - it displays fine. I've tried clear cache repeatedly and tried changing UI theme. no luck. I have 400 users and most use FF (at our request). I expect 20% of them to have restarted their PCs - so we will be getting a lot of calls tomorrow. Any help is appreciated.