We had a power surge and when the power came back up the register (Royal 480nt) displayed "EE" and I can't get it to clear. Tried turning it off, unplugging it, and nothing seems to work.

(FYI Unfortunately we only have the "OP"erator key at this time.)

mark, May 2012

You may have lost the programming. If your batteries are old, the memory will be cleared. you will need to get a key which turns to the other positions. First, try a half clear to see if it recovers. if not, you probably need to re-program it.
There is a Royal 480nt programming manual at C-tech:

http://the-checkout-tech.com/manuals/cashregisters/Royal_480nt_user_programming_manual.html

Registerman, May 2012