Sub form won't allow me to enter data (1 Viewer)

I have created an Invoices form with Invoice Details subform which was working just fine upto about 20 minutes ago. I created the necessary calculation fields which are on the form only but now for some reason I realized that the subform is not allowing me to key in data.

The subform is enabled and unlocked and is set to allow data entry but just stopped working

Any suggestions

Post a copy of your db so that we can have a look at the problem.

That's the answer. My form is based on a crosstab query.
Thank you.