I thought i should add to this to save others the same trouble i went through when the script does not fire. Consider the following scenario:
1) I created a usercontrol that holds a RadToolTipManager that acts as a wrapper for a custom confirm dialog
2) on AjaxUpdate, i dynamically add to the tipmanager's UpdatePanel ContentContainer, and set some configuration settings before showing the tooltip.
3) User clicks the Confirm button which is an ImageButton inside the UpdatePanel that exists in the ToolTipManger's tooltip.
4) A custom event that I created for the usercontrol gets called and is bubbled to the calling page...
5) Event does its thing and then I want to execute the Page.RegisterStartupScript to close the tooltip. This will not work because we are in an UpdatePanel (the update panel that exists in the TooltipManager)
So, to fix this, you must register your clientside script like this:
ScriptManager.RegisterStartupScript(this.Page, this.GetType(), Guid.NewGuid().ToString(), "CloseTooltip();", true);
Hope this helps!