Stuck in a combobox!

Upon entering the screen, I set the focus to the first field, a combobox, and after making a selection I want to tab to the next field, a textfield, but I can’t tab out of the combobox. I can use the mouse to click on the textfield and give it focus but I’d rather tab. I also tried to programatically give focus to the textfield (from the function associated with the combox’s listener) without success. Any ideas?