This is a personal bugbear which I encounter every time I reinstall a W7 OS. The problem is that when you hold the pen down – like you might when you’re trying to highlight text – Windows has a default setting of assuming that you wish to right click, which interrupts the selection you were making in an extremely irritating fashion. This isn’t a setting in the Wacom tablet settings, either, so it can be a little hard to find. The solution is in the Windows “Pen and Touch” settings (hit the Start button and then type “Pen” and you should see it as one of the options).
Pen Options -> Press and hold -> Settings -> untick “Enable press and hold for right-clicking” -> Click OK -> Click Apply.
While this may be a handy option for pens which don’t have a right-click button it really only serves to be a hindrance for a lot of Wacom users, it seems.