Barry,
It seems that with your current form and data, Image has trouble generating a pdf. Do you get this problem only with Image, or do you also get it in PlanetPress? While the data might load successfully in PlanetPress, if you go to File->Preview, and make a pdf preview, does it work? If it doesn't, then it's a problem with your form.
Another thing you could try is using the Run Locally option in both PlanetPrsss design tool and PlanetPress Image. Sometimes, depending on how they are built, some documents will not work fine unless you use Run Locally. Try that and see if it makes the form work better.
If it still doesn't work, then, perhaps you should open a support call regarding this issue. To the top left of this page, there is a "Report an Issue via the web". Click on that and follow the procedures, upload your form and your Watch process, as well as some data files, and we will be able to help you fix your problem.
Regards,
Rapha