Tooltip normally disappears automatically when mouse pointer goes outside of the note icon borders. There is a bug report saying that sometimes tooltip remains permanent, however I can’t reproduce it. If you have a reproducible scenario, please share it. Perhaps in this case it is better to record a screencast, because it may depend both on your particular project and on the way you interact with the interface.
Similar issues are commonly attributed to graphics cards, meaning they may be the result of “improper” display regeneration rather than the actual display of what a program requires to be drawn on screen.
(called “graphics artifacts”)
Do you have such problems (artifacts, ghosts) with other programs? Have you updated using your video card’s latest drivers.
You are welcome. My point was though, that you should update your video card driver, even if Dimitry is right and it is not a video driver problem, it’s good practice in general to have updated gpu drivers.