[mario]

Upgraded to 5.0.5 but the problem is still there.
Have tried in both http mode and https mode but it is the same.

In the left bottom corner of the window there is a warning about error on the page.
If compose messages in new windows is unchecked this is the error:

The error in 5.0.2 is
Line: 6531
Char: 1
Error: Invalid argument
Code: 0
URL: https: //serveraddress/zimbra/

The error in 5.0.5 is
Line: 6545
Char: 1
Error: Invalid argument
Code: 0
URL: https: //serveraddress/zimbra/

If compose messages in a new windows is checked this is the error:

The error in 5.0.2 is
Line: 16035
Char: 2
Error: Invalid argument
Code: 0
URL: https: //serveraddress/zimbra/public/launchNewWindow.jsp?skin=sand

The error in 5.0.5 is
Line: 17445
Char: 2
Error: Invalid argument
Code: 0
URL: https: //serveraddress/zimbra/public/launchNewWindow.jsp?skin=sand&localed=it

Hope this helps.

Mario