Quick heads-up should anyone run into ToolTip videos which play in Revit 2011 but do not play in Revit 2012.
In Revit 2011 ToolTip videos were not encoded in Adobe Flash format. In Revit 2012 there was a change to the ToolTip video format; they are now encoded in Flash format [so you need Flash installed in your browser to view them].
Revit leverages Internet Explorer in order to play the ToolTip videos. So if you primarily use another browser, where Flash is installed, I would verify it has been properly installed for Internet Explorer as well.
To verify if your Flash Player is installed properly, open the following address up in Internet Explorer: