Since sometime late last week, we can't log into our web admin interface with recent versions of Firefox (windows or linux). Clearing browser cache, disabling addons, safe mode, etc. has no effect. The Firefox error console consistently shows this error upon the failure:
Error: ZaApp.getInstance().getCurrentController() is undefined
Source File: https://localhost:7071/zimbraAdmin/js/Admin_all.js.zgz?v=100629122513
Line: 10768
The relevant line of script highlighted by Firefox is:
There was no problem last week, and the only thing I can think of that may have changed since then was the Firefox 3.6.8 update, although I thought that we had been able to get in last week even with that version, but can't recall for sure.

Internet Explorer works fine, and some older Firefoxes we have casually tried around the office (3.0.x) work fine.

Our ZCS had been 5.0.20, but last night I updated to 5.0.24 in hopes of resolving the issue, but it didn't change anything.

Any ideas on where to look next would be appreciated. Thanks!