If you go to System -> Enterprise Parameters, the Directories URL should point to http://a.b.c.d/CCMUser/xmldirectory.asp using the IP address rather than the server name. Make sure that field is correct.
...and if that does not work, you MAY need to reload 3.05a AFTER disabling SNMP services in Windows. I did the upgrade recently and lost our global directory completely and had to reload the the OS (Win2K), the old application (3.02d), and then reload the good BU I had with the global directory, then upgrade to 3.05a after SNMP was disabled.
FYI, what is a resolution to the problem is that the procedure for correctly upgrading to Cisco CallManager 3.0(5a) has a Read Me First document located at http://www.cisco.com/cgi-bin/tablebuild.pl/callmgr saying that the SNMP service should be stopped just prior to installing the executable 5a upgrade. Reading through this file and following the instructions will insure that the DC Directory Server upgrade will function correctly and the user directory should be intact post-upgrade. Between that and my initial response, the Corporate Directory selection should be both listed and function properly.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.