Rather depends on what's on the surface underneath.If its good and dry gloss paint try white spirits or meths.If its emulsion I think you will have to scrape or sand off when hardened and repaint.If its wall paper as for emulsion and repaper the affected area
Well are you not going to decorate the walls? if so why is a small area of adhesive a problem, just chipp it of and sand a little, and then decorate, don't tell me you have just stuck the dado to the wallpaper.??????