Internal Hard Drive Locked "Read Only"

Hi, I'm locked out of the internal hard drive of my Macbook Pro running Mountain Lion….although I can access the repair (CMD+R) partition on the internal drive and alternatively boot from a USB thumb drive Mountain Lion installation, the main partition on the internal drive remains locked. I cannot select it to reinstall Mountain Lion or even backup files via FireWire disk mode (drive does not appear on host computer)

When clicking on the graphic image of the internal disk to which I'd like to reinstall OS X a window pops up saying, "This disk is locked." ('Disk Utilities' are unable to repair disk/permissions)

In Terminal when running from the OS X repair partition before the cursor occurs this text: -bash-3.2#

Can 'read only' permissions be changed via Terminal commands executed from the OS X repair startup (CMD+R)?

chflags 0 /volumes/volumename

nothing happens…just returns cursor after -bash-3.2#

chown 0:80 /volumes/volumename

returns: chown: /volumes/volumename: Read-only file system

chmod 775 /Volumes/Volumename

returns: chmod: Unable to change file mode on /volumes/volumename: Read-only file system

chmod -N /volumes/volumename

returns: chmod: Failed to clear ACL on file /volumes/almathea: Read-only file system

thanks!