After some issues with a NFS share I noticed that a couple of VM’s changed to Invalid. The VM was still fully operational but vCenter didn’t recognized the VM’s anymore.
I found the following knowledge base article: http://kb.vmware.com/kb/1015778 which describes the following symptoms:
•Virtual machines display as invalid in vCenter Server
•The command service mgmt-vmware restart fails to stop the management agent
•The command vmware-cmd -l returns the error:
PANIC: SyncWaitQ: The system limit on the total number of open files has been reached
•The command ps -auxwww shows a large amount of SSHD processes running
In my case the solution was to restart the management agent on the host where the VM’s where running on.