
4 answers

Are you Enterprise or Unlimited edition of sfdc? If so, a record type allows you to create different page layouts and have picklists that present different sets of values to different user profiles.
Check the following:
Setup...App Setup...Customize...Opportunities
Do you see an option for "Record Types" under the Opportunities menu? If yes, click on it to see if there is more than one recordtype. If yes, click on the recordtype label name. You'll see all the standard and custom opportunity picklists. Click the Edit link next to "Lost Reason". If "Client deferred" is in the available values box, move it to the Selected Values box.
If you are using Professional edition and don't have access to record types, I'm sorry but I'm out of ideas.
Aiden