What are your form properties for .DisplayErrorDialog and .DisplayErrorProvider?

Not 100% sure about this (too lazy to look at the help), but I think you need to have .DisplayErrorDialog set to true when your business rule uses this.AddBrokenRule. Similarly, if your form has .DisplayErrorProvider set to true, then your business rule class should be using this.AddErrorProviderBrokenRule.

Of course, I could be wrong.

Mike

Thought I'd read the help a little before I pressed "send" - check out the help topic "Displaying Broken Rules and Warnings in Windows Forms"