On Vista and Windows 7 the tool tip keeps flickering and the CPU usage rises. I beleive there is a problem with the mouse move event and tool tips which cause a mouse event to be continually fired. The solution is to check to see if the tooltip tect has changed before setting the text again. The attached file patches all the places SetToolTip is called to solve the blinking.
There is bug open for this issue, ID: 2694674