Zimbra Open Source 7.2.1 GA.

When I log into the web client from my office (behind a web proxy) and go to the Briefcase and try to open an attachment by double clicking on it, a docx Word document for example, I get

Unable to connect

Firefox can't establish a connection to the server at https://mail.myserver.comhome

On IE the page just never displays anything.

The URL that is given is https://mail.myserver.comhome/myname@myserver.com/Briefcase/Word-doc.docx?ver=1

If I manually fix the URL by removing the "home" part, the document opens fine.

https://mail.myserver.com/myname@myserver.com/Briefcase/Word-doc.docx?ver=1

Where is the "home" string being injected into the URL and why only on the web client?

Zimbra Desktop (running on a PC on my the same LAN as the Zimbra server) does not exhibit this behavior, and neither does the web client from the same PC.

I'm stumped.

Thanks for any help
Daniel