I log into a Zimbra server for email. I may be logged in on the local network, from outside, over the Internet, or across a VPN. The hostname is always the same. I found that I would have to actually quit Firefox in order to log back into Zimbra if I initiated a session over the Internet, and later made a VPN connection. I would see a white screen with a link in the upper left corner which said [Sign Out]. Clicking it did nothing. I actually had to restart Firefox. I discovered that this happened because of Noscript’s ABE protection. I did not wish to disable this, as it is a useful security feature. The solution is to go into the NoScript options, under ABE, and edit the SYSTEM settings. It normally says
# Prevent Internet sites from requesting LAN resources.
Accept from LOCAL
I added this line after the Accept lin:
Accept ALL from *.<mydomainname>
That fixed the issue. It might be advisable for people who use Noscript in a corporate environment with VPN access to add this to their ABE settings in order to prevent web application failures.