Masters gone from ALL MASTER SERVERS view

Hi gang,

Need help with solving this puzzle. I have two masters (NBU 7.1.0.4, OS SLES 10 sp3) that from one day to the other are not being displayed on the ALL MASTER SERVERS view in OpsCenter (v7.5.0.6, OS WIN2K8R2 sp1 64bit). I have looked into ViewBuilder, and their are showing up now as Object Type: Media_Client, while the other Master servers are: Master_Media_Client.

Any ideas on what happened here? And, what can I do to remidiate?

Thanks