Infopath - Cannot submit form

Hi,
New to K2 and infopath so hoping I can get a bit of help on this problem:
I created a form in Infopath, published it, and created the corresponding K2 process. Everything worked fine. I then modified the form extensively, re-published (by overwriting) and lost the ability to submit the form (the button was missing). I found on these forums to refresh the form, or redo the form settings, this got the submit button back but now everytime I press it to submit the form I get this error:

InfoPath cannot submit the form
An Error occurred while the form was being submitted
The form definition (.xsf) has an invalid mapping from the document to the submit Web Service.

I've tried deleting the sharepoint site it's bound to - re-publishing, re-exporting the k2 process, refreshing the form, and re-doing the settings, and every permutation thereof.

Thanks in advance!
-Ian