Attachment Category

I changed the name of the attachment field called 'Resume' in the Candidates module to 'CV'. This has caused a problem because when I look to assign the Attachment Category in my email template, CV isn't available. I guess there is some mapping going on and Resume needs to exist. Therefore, I tried to rename CV back to Resume. System says Resume already exists and won't let me,Tried to create a new custom field - same problem. Now stuck in a loop that I can't resolve and need some help please.