Hi mattmeyer,
as per the issue for Evangelos...
Your issue is that you are submitting back an XDP format and not the PDF format. To resolve this issue, open your form and select the FSSUBMIT_ field from the heirarchy. Click on the Object palette and look at your Submit options. On that tab look at the Submit Format dropdown. You will want to choose PDF instead of XML Data Package (XDP). I have attached the working version of your form!!!
Basically you where reconstructing the PDF with the submitted data (the data does not have the signature in it) and hence the signature was being lost. The signature info is only part of the finished PDF.
NOTE: that the signatures will break from step to step (i.e. a yellow exclamation mark will appear) but Adobe are aware of this, and it will be fixed in the future.
regards
David.