InfoPath Dev

I can publish it, but when I go to Submit it, I get another error. "Infopath cannot submit the form"  Details: InfoPath cannot submit the form. The form was not submitted because a form named Form.xml already exists in the document library at [URL]. Please contact the provider of the form.

I'm trying to create an InfoPath form for publication on a SharePoint site. I create the form and run a design checker. Get no errors. Select Change Settings, highlight Compatibility (auto) and select Web Browser (auto). I enter the main part of the URL. I get an error "Could not verify the form template on the specified ...