failure on 'pg_ctl stop' command

Hi Everybody,

I had a failure on stopping postgres.
The command I issued was:
>> pg_ctl stop -m s

and its response was:
>> waiting for server to shut down............................................................... failed
>> pg_ctl: server does not shut down

I repeated the same command and the response was identical.
I proceeded to issue:
>> pg_ctl stop -m f

and this time it came back with:
>> waiting for server to shut down.... done
>> server stopped

Would somebody please tell me what this means?
Is it indicative of some trouble? What can/Should
I do to remedy the situation?

My environment is Redhat Linux, Dell AMD 64bit machine
with postgres 8.2.4.

Regards,

Tena Sakai
tsakai(at)gallo(dot)ucsf(dot)edu