I recently upgraded my Zimbra from Version 7.2.1 under Ubuntu 10.04 LTS x64 to Zimbra 8.0.1 under Ubuntu 12.04 LTS x64.

Steps I've done:
  1. Full system backup
  2. Backup of /opt/zimbra
  3. Release upgrade to Ubuntu 12.04 LTS
  4. Updating Zimbra to Version 8.0.1
  5. Final system reboot

Now I've seen two problems in the new installation.

The first one I saw is that the Message preview was active, but the setting showed deactivated. So I activated it and deactivated it again.
But when I open a message not only the popup openes with the message inside, also the preview window opens on the bottom of the message list.

The second more bigger problem is that I can't send any new E-Mails (replying works).
When I click on New E-Mail the popup window opens but everything stays gray and I can't click anywhere, but I can Tab through the input fields and can enter text into them.
Also the button bar at the top covers a row. I attached a screenshot with it.

If I disable the option to compose new e-mails in a new window nothing happens when I click on new e-mail.

For testing I used Google Chrome 23 and Mozilla Firefox 16.

Thanks for your Help!