I was testing the new Duplicate Detection feature in MS CRM 4.0
I wanted to be warned about duplicates that might be entered as a Contact with the same name and phone number of an existing Contact. I created a new rule that looked for an exact match on Full Name and Business Phone. Through testing, the duplicates were not detected as I entered new Contacts with seemingly the same name and phone number. Initially I thought that, maybe there was a 'latency period' for the newly published rules to take effect, and tried again a little later.
The problem was that I was testing the Contacts Full Name. Since the record is not saved until after the duplicate detection work is done, the Full Name attribute was empty. I had to back up and modify the rule to test for the discrete Last name and First name fields. Once I made this change, the duplicates were detected.
Tip: Since the match codes are updated every 5 minutes, there is still a chance that duplicate records will sneak in, if entering several records in succession.
I also ran into a problem, where the duplicate detection rule "fired", but it seemed to get stuck in some loop, and never returned the form that challenges me choose whether I want to go ahead and add the record anyway, or cancel out. The security roles for users, need to have the "Duplicate Detection Rule" set properly (ie NOT 'None Selected') for the duplicate detection function to process fully. Once I fixed this in the roles, duplicate detection worked all of the way through.