mount: /dev/hda5 already mounted or /mnt/FC3 busy-??

[John Cox]

My ubuntu install is on hda2. When I try to sudo mount -t ext3 
/dev/hda5 /mnt/FC3
I get:
 /dev/hda5 already mounted or /mnt/FC3 busy
and I can't figure out why. As far as can tell hda5 isn't mounted and
I don't know what /mnt/FC3 being busy is all about so what is causing
this? Could this be due to the Fedora partition being set up as a
logical vol.?
I can mount hda1 without any problems.

Can someone tell me what might be causing this?

   Device Boot      Start         End      Blocks   Id  System
/dev/hda1   *           1       18281     9213246    7  HPFS/NTFS
/dev/hda2           18282       32512     7172424   83  Linux
/dev/hda3           32513       32720      104422+  83  Linux
/dev/hda4           32720       77520    22579326+   f  W95 Ext'd (LBA)
/dev/hda5           32720       77520    22579326   8e  Linux LVM