I have installed Zimbra 6.0.7 Open Source in Ubuntu 10.04
The service stop each 5 days aprox.
In the client web interface show "network service error has occurred"
When we restarted the zimbra services (zmcontrol stop / start) all is ok .
I think is a ldap problem.
this is the errorr message from the mailbox.log:
.....account - unable to get addr by alias domaincom.zimbra.common.service.ServiceException:s ystem failure: ZimbraLdapContext