E6900 domain hanging

SC Version: 5.19.3 Build_01
Version build: 1.0
Version String: 5.19.3
RTOS version: 45

when I do "showkeyswtich"
Domain A keyswitch is : on
Domain B keyswitch is : on
Domain C keyswitch is : on_to_on
Domain D keyswitch is : on

when I do "setkeyswitch -d c off
"setkeyswitch operation did not complete
Cannon perform keyswitch operation while keyswitch is in progress.

"Showboards" shows that state is Active and Passed for all domains.

Domain C is totally inaccessible, and OS is down in domain. However, Domain A, B, and D all are running critical OS instances and they all up and running.

I'm thinking of doing "reboot" in SC, but afraid it might affect the running domains. What do you think ?

---------- Post updated at 07:29 AM ---------- Previous update was at 12:55 AM ----------

UPDATE:

I did a "reboot" commnd from SC..this is the response I got:

"Waiting for critical processess to finish. This may take a while"

and no change happened...SC still accissble, but can't access the domain c shell.

As per customer, this problem started when he rebooted the OS on domain c.

I checked the Service Manual(817-4120-13) for SC, and it says clearly:

So I don't want to initiate a hard reset while the other domains are up, especially that it is a very critical production domains that are up (luckily the domain that's down is a testing domain).

Any clues ? I'm thinking of taking a down time..or maybe log a case with Sun.