popUpButton is setEnabled:YES but doesn't allow click

my popUpButton is in a window with a group of popUpButtons. If I try to click the 2nd of 4 vertically aligned buttons then the popdown menu will not appear. If I select the 3开发者_JS百科rd or 4th then the 2nd will now be selectable.

throughout my code the setEnabled on that popUpButton is :YES.

ideas on where to look in my controller?

This is a Objective C/Cocoa Question.

the solution was in the -validateMenuItem code... I wasnt checking for a return value of null somewhere that method and it was logically returning false.