We have a HA Hyper-V cluster with 8 nodes that we are backing up VIA DPM 2010. As far as I can tell it is up to date with all the latest patches and the like. Most things seem to run fine, however, when I try to create a new protection group or add members to an existing one several of the VMs do not appear in the list. Any ideas what might be happening here?
Are the VMs running as cluster services? Open Failover Cluster Manager and make sure all the VMs are there. If you create a VM in Hyper-V Manager it is not clustered, you must later add it to the cluster with the Failover Manager.
Also have you installed KB975354-v2 on the Hyper-V Servers?
Also are you using the Release Candidate or the RTM? If you have RTM, did you have the RC installed before?