Cannot report on a particular master server

OpsCenter Version: 7.5.0.7 OS: Windows 2003 NBU Master Version 6.5.5 Key details - The master server is displayed on the main Monitor screen as connected - The master server does not appear in the data collection screen - The master server does appear in the Agent screen (I have deleted/re-added the agent successfully) - I am able to drill down into the master server jobs, drives, media summary, etc from the monitor screen - I am unable to remove the master as it does not appear in the list to remove - I am unable to re-add the master because it already exists - It does not have any aliases - I have re-installed the agent on the master server, restarted all services (NBU & OpsCenter) - I am a security administrator in OpsCenter The master server is setup identically to all the other master servers in our environment and only this master is affected. Has anyone come across this issue before? Any assistance would be appreciated.