Wacom Driver Tips
Problems with pens clicking while hovering/not in contact with tablet
Common problem, pain in the butt, related to pen sensor mis-reporting pressure, Wacom would love for you to buy a new pen, but you can work around the dodgy pen sensor a little, with some loss of resolution in the pressure reading.
Open Wacom Preferences, Ctrl-Click on "About" brings up the tablet diagnostics. Move the pen close to the tablet to get a reading from it. The number you're interested in is the "Pressure" reading, a working pen, this should be 0, a dodgy pen will misread a higher number, take note of the highest number it reads and add a margin on top of it (say 20-40).
Next, we're going to edit the file %APPDATA%\WTablet\Pen_Tablet.dat, open it in Notepad++ or something that can handle Unix line endings. It's a XML format, we're looking for the setting under "PressureSafteyMargin" (the misspelling is intentional, that is the actual name of the setting). There are two matches for this, the first is the transducer for the eraser, the second is the tip, under the tip one, put your new margin in the XML. The line should look similar to the following when done, with where I have 300, you put the margin you got from the Wacom Preferences app, plus your additional 20-40: