Symptoms

When you configure the "When form passes validation" rule on a form, the "tooltips" on the controls gets displayed when running the form "directly" during runtime. But, when you host the form inside SharePoint 2010, the "tooltips" does not get displayed as expected. Using "other" browsers is working as well.
 

Diagnoses

SharePoint "forces" IE to run in "IE8 document mode" and this is what is "breaking" the tooltip functionality. Using the browser developer tools, we found that everything works as expected when switching the document mode to IE9 or higher.
 

Resolution

It was suggested that we editing the SharePoint master page. Instead of forcing SharePoint to use IE8 document mode, you can force it to use IE9 document mode and then everything should work as expected.