Right answer, not quite right approach to the solution. Inexplicably, using the Terminal to delete the appropriate file kept telling me that "file not found". So, I manually navigated to the folder, found the file that needed to be deleted, dragged it to the trash and, voila, everything worked. Sometimes the terminal just doesn't like to work like Unix. In any case, many thanks for the suggestion. It led to the solution of the problem and all is well again.
mrf