Beth,
I assume this is because of a field size setting, or validation rule
(set at the table or form level), or input mask (set at the table or
form level), or macro or code running on your form, possibly on the
Before Update event of the postal code control, which is restricting
acceptable entries. You will need to track down what is causing the
restriction, by looking in the various property settings etc that I
mentioned, and adjust accordingly.
- Steve Schapel, Microsoft Access MVP