I see your running v5b3 -briefcase isn't what your looking for?
/blog/archives/2007/08/zimbra_briefcase_1.html
-better WebDAV support is also a v5 thing (
/forums/administrators/11171-webdav-briefcase.html#post58137)
(and shared mail folders so people don't have to do my old rss feed workaround
/blog/archives/2007/08/shared_folders.html)
EDIT: so did you just change your version string?
it now reads: Release 4.5.6_GA_1044.DEBIAN3.1 DEBIAN3.1 FOSS edition
I swore it just read v5 BETA 3
+ it shows your 'Viewing User Control Panel'
heck you even have a thread:
/forums/administrators/11232-zimbra-5-0-beta-any-debian-build.html
-of course my eyesight could be going; but I would hope not to that degree so soon!