ERROR: doesnt attach file in ajax session

[angelinux]

Hi, this is my first post I have an error, attaching file.
My Zimbra version is 5 and is in DMZ zone, When I start session and select advanced ajax I can not attach files with any browser, but If I start session from external network (internet) I can attach file without problems.

Internally I have this error when I try to attach files:
method: AjXmlDoc.loadFromString
msg: End Tag 'head' does not match the start tag 'meta'
code: AjxException.INVALID_PARAM

[angelinux]

Anyone have idea about this error??

The next day, the problem was solved and nobody do anything.
What was the reason??