This is a Java script error that has causes such as these:
Domain Name System (DNS) resolution failure
Browser or Graphical User Interface (GUI) bugs
Browser Java client version incompatibility issues
A problem with specific cached pages on the Cisco CallManager server.
In the first three cases, a more general error is likely, such as not being able to load the Cisco CallManager Admin page.
To resolve issues, refer to these procedures:
To resolve problems with specific cached pages, perform these steps:
Restart Internet Information Server (IIS) on the Cisco CallManager server on which you wish to add the voicemail ports.
When launching the Cisco CallManager Admin page, use the IP address of the Cisco CallManager server, rather than the hostname.
To resolve DNS issues, ensure DNS is working properly. If appropriate, test with an IP address instead of DNS name.
Java client incompatibilities. If only non-console PCs accessing the Cisco CallManager Admin interface through the browser see this issue, then Java incompatibilities could be the problem. This situation has been seen more commonly when running Windows XP. For problems with browser-Java client compatibility, upgrade the browser's Java plugin to a recent version of SunJava VM.
Bugs. If all of the previous solutions fail to resolve the problem, open a service request with Cisco Technical Support.