We are experiencing an issue with users occasionally being unable to download attachments. They click on them, and the browser prompts to save the file, and yet nothing happens. (it just "spins")

I am running the latest version of Zimbra (6.0.6_GA_2330.UBUNTU6)

This has been verified on several workstations running Windows Vista, XP, Server 2003 (terminal servers), Ubuntu 9.10, 10.04, and on Firefox 3.x.x AND IE7/8. So I am fairly confident it's not a client end issue. Clearing cache doesn't help. It doesn't happen all the time but when it does, nobody can download that particular attachment. (i.e. forwarding to another Zimbra user doesn't allow it to be opened.)

It happens mostly on PDF files, but has also happened on .doc and .xls as well. Forwarding the message to Yahoo! or Gmail allows the attachment to be downloaded no problem.

Unfortunately I have no /opt/zimbra/log/mailbox.log to check as it has been blank for weeks as reported in this thread.

Because of these two issues I am getting very frustrated with Zimbra right now! I would love it if anyone had suggestions because searches of the forums, wiki, and bugzilla have revealed nothing so far.