Hi,
we partiality solved this problem, we recovered the html version of zimbra's web-mail.
First in a test machine we install a fresh copy of zimbra 6.06 opensource and found several differences in the contents of the folder
/opt/zimbra/jetty/work/ (Attached in diff.txt)
Following an older post:
mobile calender Internal Server Error
We decided to take the next actions:
zmcontrol stop
rm -rf /opt/zimbra/jetty/work/*
mv /opt/zimbra/log/*.log /var/tmp/
zmcontrol start
Doing this we fixed only the html version, but we still have error 500 on the mobile version.
Any ideas?