URGENT - cannot revive user account!

OK, so I've been messing around for awhile trying to change my shortname on my account for awhile now. I changed the full name the way I want it - CDB - but the short name is still incorrect. When I went into the Finder under Users to change it the same way I'd change a folder name, it is grayed out and I am unable to edit (even after unlocking to make changes).

I followed these instructions TO THE T: https://discussions.apple.com/docs/DOC-3872

However, when I go back into the Finder and grab "PCP (Deleted)" - my old short name - and try to change it back, it is STILL GRAYED OUT! I can't change it back and therefore can't revive my user name using the above method. UGH! I don't know what else to do! Technically I haven't lost any info or apps, but I will have to go through and reset everything. Not the end of the world but still annoying.

Help appreciated!