Hi Michaelc,
Sorry to hear about the trouble.
There are couple of possibilities that after saving the form it isn't editable-
1- If you have added signature to the form and then saved it, then you can't edit it again. As adding the signature to the form is last step which makes it secure so that it would not be edited by anyone.
2- The person who created the form or own this form has to save this form as "Reader Extended PDF" so that the form can be re-edited after saving. This can only be done by the owner of the form.
Or as a work around you need to re-download the form and start all over again.
For detailed description please read this- How to edit fields in PDF form after saving
Hope this helps!
Regards,
Akanchha