Hi Catharine,
Sorry to hear that you're having trouble on your forms. Below are a few questions:
Is this the error you're seeing?
"The form cannot be filled out because you do not have adequate permissions, another user has the form open, or the form is open in another program. Do you want to open a read-only copy of the form?"
What happens when you select yes to open on read-only? Can you still fill out and submit the form to SharePoint and DBXL?
Are you using check-out/check-in when editing the form in SharePoint?
Using the SharePoint set up you have provided us from another thread (http://www.infopathdev.com/forums/p/16553/58130.aspx#58130), I click in and out of my forms constantly when testing and have never gotten this error while reopening forms.