I had the same problem. The Schedule C is corrupted. First use the forms menu to open the form and print what you have. Then delete the form. Then open a new schedule C and start filling in the entries. If you look at the list of forms you will see that any 1099s that had been linked to the Schedule C are marked as having errors. You need to open each one in turn and link each 1099 to the schedule C by typing in the Schedule C name. When completed all the entries should match the copy that you printed. I found it easier just using the forms menu directly than going back to the step by step method.
