Problem:
Had a driver call and say they cannot enter PO on the handheld after the upgrade to 6.1. Is there a setting for that I need to change?

Solution:
Try going to list>routes>handheld class>Sales Rules 2

Drag the buttons from the Hidden to Displayed to allow the PO number to be entered.  This is the REF# button.  Hit modify and hover over the buttons for an explanation.