Since no one else has replied yet, I'll take a shot. My first guess is you are not a sysadmin. Try one or both of these for more clues:
a.) Use the Wizard to access the same options - from Enterprise Mgr...Tools, Wizards...
b.) Run sp_replicationdboption 'pubs', 'publish','true' assuming you have a pubs database, or some other test database.
My guess you'll get a security error. I've got 10 yrs experience with Repl in SQL 2000 and never seen this issue, but I'm a sysadmin.