Backup error says "Missing or Invalid credentials for esxhot.domain.local
Several potential causes:
Update the host credential: Reneter the credential for the host(s) in vRanger inventory.
If error happens immediately after upgrade, see VMware KB article: http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=1024235&sliceId=1&docTypeID=DT_KB_1_1&dialogID=101446216&stateId=1%200%20101448469 .
Note also, AD integrated ESX hosts are not yet supprted by vRanger.