Read-only file system not actually read-only?

[Craig Emery <fedora-test cemery org uk>]

I'm running FC2T3 and am trying to build courier-imap as an RPM.
I've gotten to the position that I can't delete the 
BUILD/courier-imap-3.... directory.

The error is:

rm: cannot remove `/home/cemery/rpm/BUILD/courier-imap-3.0.3': Read-only 
file system

This is what mount (1) says:
/dev/md2 on / type ext3 (rw)
none on /proc type proc (rw)
none on /sys type sysfs (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
usbdevfs on /proc/bus/usb type usbdevfs (rw)
/dev/md0 on /boot type ext3 (rw)
none on /dev/shm type tmpfs (rw)
/dev/md6 on /home type ext3 (rw)
/dev/md4 on /tmp type ext3 (rw)
/dev/md3 on /usr type ext3 (rw)
/dev/md5 on /var type ext3 (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)

So you can see that everything is mounted rw, though all my partitions 
are RAID1 ones.

Running lsof doesn't show any busy files in that directory, so that's 
not it.

Any ideas?

TIA

Craig.