Goto:
    http://www.telerik.com/DEMOS/ASPNET/Prometheus/ToolTip/Examples/ClientSideAPI/DefaultCS.aspx

Do the following
    Don't move the mouse over the Submit button
    Click on the E-Mail text box
    Tab until you reach the Submit button

Thanks,
Italo

Hello Italo,

Thank you for your feedback. We highly appreciate it.

The js error is result of having no mouse cursor on the page and therefore the position at which the tooltip should be placed cannot be calculated correctly. If you set the property RelativeTo="Element" of the corresponding tooltip the problem will no longer exist as the position of the tooltip will not be calculated relative to the mouse which is its default value. This is a bug in RadToolTip control and we will do our best to fix it for one of the next updates of the control.

Please, find your Telerik points updated.

Kind regards,
Sophy
the Telerik team