During a backup to NAS device last night, one of our servers quit talking to the NAS box. A MUP event 139 was logged on that server. The server was running Symantec Backup Exec 2010 R3.
I backtraced the reason for the failure: the domain controller the NAS uses for authentication of SMB clients ran out of disk space, and quit being a domain controller. I fixed that probem and rebooted the domain controller.
On the server which had the connectivity hiccup, I can ping the NAS device by IP address, netbios name, or by FQDN. However, if I try a net use \\<device name>\share (which uses NETBIOS), I get a windows event 53. This works correctly against an identical twin NAS.
Further, I can connect to the NAS that the server can't using netbios and other domain members.
I did reset Symantec Backup exec by restarting the Backup exec services (since the backup job wouldn't quit nicely). The server in question is a physical machine (not a VM).
It is not a firewall issue (as Microsoft seems to imply)-I disabled Symantec Endpoint Protection 11.06a (which the server is running).
I rebooted the NAS box, also. How can I clear up the Error 53 condition without rebooting the server?