This issue has only started since I upgraded from 7.2.4 to 7.2.6 when the security vulnerability was announced.
I have 2 machines, both running 64 bit linux and : Zimbra Desktop 7.2.2 GA (build 11951)
The server is now running : Release 7.2.6_GA_2926.UBUNTU10_64 UBUNTU10_64 NETWORK edition.
Intermittently (could be 2 hours, could be 5 days) my Zimbra desktop instances simply stop receiving updates from the server. They don't indicate they are offline or there are any communication issues usually, they just stop getting anything new. I have a thunderbird instance via IMAP and a BES that both keep on getting mail, so it's just isolated to ZD.
A simple close and restart of Zimbra desktop sees things off and running again, but prior to the 7.2.6 upgrade I just never _ever_ had to do that (like session times exceeding 100 days with no problems).
I've been unable to find references to anyone else having this issue, and I can't find any relevant bugs. Unfortunately, I also can't collect any information that seems to be relevant that might allow me to file a bug report, so I ask here to see if anyone else is seeing this with enough variability to help narrow it down.