After the Zimbra upgrade from 5.0.8 to 6.0.7 some users are reporting visualization issues.
Using Mozilla Firefox, the first time they login into their account, zimbra appears with the reading pane in the right, even after they changed to bottom. If they logout and login again, everything appears like they want.
They logout and after a few hours, they login again, zimbra turns appearing again with the reading pane in the right (3 columns layout)...
Why ? how to resolve this ?