I had a request from a user to modify an InfoPath Form template, which I did, and it worked perfectly in my development environment. When I went to update the existing form in my test environment, the installation got stuck. So I removed the existing template, and re-installed the it.
That fixed the form, and I was able to create and edit new forms, but existing forms that used the old version of the template no longer open. When I click to open them, I get the following error message:
The following location is not accessible, because it is in a different site collection: https://testServer/FormServerTemplates/MyModifiedForm.xsn.
All of my changes are cosmetic, I just created a new view that displayed the text in an expression box rather than a text box. (due to scroll bars, the form was printing badly)