[PLUG] question on sudo umount command

[logical american]

Hello:

Recently one of my commands

[linux ~]$ sudo umount /dev/sdd2

failed to return back to the command prompt, and all subsequent sudo 
commands failed similarly.  Only by rebooting the system was I able to 
get the "sudo umount /dev" command working again.

I am running 64 bit openSuse v13.2 linux kept to current revision level.

Any ideas on why umount is not returning to the CLI prompt?

Randall