It helped, but didn't fix it:
Upgrade issues - zimbraMailUrl
When I restart mailboxd, there is the problem again.
I'm editing /opt/zimbra/mailboxd/etc/jetty.xml.in and zimbraMailURL is set to /zimbra, but anyway when restart services, the login banner is missing, as tab icons and folder images.
Running: Release 6.0.1_GA_1816.SuSEES10_20090911162123 SuSEES10 NETWORK edition.
I already posted a support ticket, but the team hasn't been able to solve this issue in about a month.