Well, it wasn't bound to an integer FK (just to a text field of a local table), but the solution certainly worked! If that's not one of the most amazingly remote solutions... I wonder who originally thought of adjusting the column's inputmask to solve this?

Actually, it is not so amazing when you stop to think about it. The column's ControlSource is used to update the value of the combo box. But a combo box also has a DisplayValue. If the DisplayValue is wider than its value, the value will be truncated without an InputMask to tell VFP that the display needs to be wider.

FWIW, I am prestty sure that this is only an issue for combo boxes with style=0 - drop down combo. It is not an issue for drop down lists because they do not have a portion that accepts text.