I was trying to set up a couple of comboBoxes for a custom ExtJS triple input (Month/Day/Year) datefield and the comboxes would display but be cropped to 17px. No matter what the width i set on the control, the boxes would not display right. I tried a few things and finally realized that i had specified a “hiddenName” property to be the same as the field’s ” id” property. If such is the case, make sure to specify a unique “hiddenId” property and your comboBoxes will display fine.