I've got a workbook with one sheet that is misbehaving. When I try to set up a validation list, the dropdown arrow does not appear when the cell is selected, and the cell does not function as a dropdown. This is true no matter what cell I try on that sheet. All of the other sheets in the workbook work fine for validation lists. Is there a sheet setting somewhere that would disable validation lists? (Protection is turned off on the offending sheet).