set to root and it can't be changed, neither can the perms.
irrespective of the automount system, as root nothing should stop you to change grps etc, unless you have mounted the drive read only
As a temp fix you could type commands as root (once drive mounted)
and get inspired to mount manually the drive somewhere else
You may want to look at the /mnt permissions
Not using fc5 either. In MDV level of security affects the mounting of usb drive.