Crap.
Yeah. I forgot that the validation routines use that set of data, and failed to notice the validation error when I tested the change. <img src="https://www.ubbcentral.com/boards/images/graemlins/frown.gif" alt="" />
The fix is to remove line 652 of cp2_vars.cgi.
*edit* Filed as bug 9401.
If anyone's experiencing this bug and would like it fixed, please open up a
support ticket, and I'll update your site. You must enter your FTP and admin information in the ticket. I am not going to mail the file.