Hi Kathryn,
Hope you've managed to solve it earlier, anyway I'll point to the most possible cause, it might be still helpful.
The article
Developing widgets describes the steps needed to include properties of the original webpart in the widget as well:
6. The Properties tab includes all the properties available for the parent web part. You can notice that all of them are disabled by default. Using the Display attribute in the editing form check box you can choose which property will be available for the widget's user. Please bear in mind that any change must be confirmed by clicking the OK button.I suppose this was (is) the missing thing here.
Regards,
Zdenek