Hi,
I have encountered the same problem with the blank screen at the admin login in a vserver setup on a Debian box. In addition the spell package won't properly install.
In my vserver installation the problem was the missing /etc/hosts file with the localhost entry. Therefore the mnemonic name "localhost" couldn't be resolved in the vserver, which is heavily used by Zimbra. After creating /etc/hosts with the localhost entry and reinstalling Zimbra, everything works fine
.
Greetings, Kastor