The settings that you have in your runtime have to be specifically set and do not just carry across from your Development that you have set in Tools | Options.
>I just checked the form's datasession setting, and it was set to "1 - default", so that's not it. I haven't made any changes to the forms or code since upgrading from VFP7, and it worked fine there. And it works fine on my computer. Just not on any computer that runs in the runtime environment.