pg_ctl stop failure

8.4.13 & PostGIS 2.0 on Red Hat 6

I want to do a offline backup of /var/lib/pgsql/data

But whenever I do

Pg_ctl stop

I get

-bash-4.1$ pg_ctl stop
waiting for server to shut down............................................................... failed
pg_ctl: server does not shut down

1. If I do

pg_ctl stop -m f

the cluster and databases shutdown as required but is this a clean and/or consistent shutdown of the cluster in the
sensethat I could recover from the OS  

cp -r /var/lib/pgsql/data

command that I did?

2. Any ideas as to what could be causing the pg_ctl stop command to fail. I tried doing it again after a -m f stop
followedby a pg_ctl start but still no good. 

Thanks

Austen Birchall
DBA
Met Office