As I noted in the thread, http://www.zimbra.com/forums/error-r...-work-mac.html, offline functionality seems to be working okay for Macs even when they are accessing shared folders. (ZCS 5.0.12 NE Mac OS 10.4; ZD 0.92 build 1433 Mac OS 10.5)
However, things are still a bit odd for Windows. When I had ZD 0.92 (1433) for Windows open I accepted a share invitation, then disconnected the network. ZD basically stopped working at this point: I could still see folder names in the left panel, but clicking on them didn't change the contents of the upper right panel.
Closing and reopening the ZD window didn't help. Neither did restarting the service via Control Panel > Administrative Tools > Services.
What does seem to work is right-clicking on the zimbra icon in the Tray, choosing quit, and then relaunching Zimbra. The shared folder(s) aren't accessible at this point, but all of the user's own folders seem to be fine, and mail can be composed/placed in the outbox. When the connection is reenabled, access to the shared folders is restored and mail in the outbox gets sent.
So essentially what I'm seeing right now is an annoyance with a workaround. (Outside of access to shared folders while offline, which might be nice but isn't necessarily something someone would expect.)