I've had this problem recently,
My Wacom Bamboo Pen & Touch tablet wouldn't stop glitching/lagging around the screen whenever I pressed to drag... which was horrible and making it prone to useless.. and it is not my computers' specs fault, although it does run windows /joke ..
So I tried Google! since Google always has the answer.
Read more on http://variable.dk/blog/394-stop-a-wacom-bamboo-pen-touch-tablet-from-glitching-or-lagging-on-windows