Lately, sometime when we download an attachment from advanced GUI, everything looks ok but we get corrupted files with wrong size.

Where in zimbra I can found some evidence if the problem is int the server or not?

I checked zimbra, mailbox and jetty logs, but nothing wrong there.

It is Release 5.0.15_GA_2851.RHEL5_64_20090310170650 RHEL5_64 NETWORK edition