My Wacom Intuos2 has suddenly stopped working. The power is on, and the light is shining it's usualy oragne-red. However, when I bring the my tablet pen close to the tablet itself the light would remain red, or flash green. I recently moved and my tablet was working fine before then. Thanks!

SOURCE: My Wacom Intuos3 tablet won't switch into pen mode

I had the same problem with my Intuos3 on Vista. Tech support suggested the following.

Do this.....Go to Start--->control panel---->system(in classic view)---->device manager--->click on "human interface devices"--->then click on "Wacom virtual HID driver" and right click on that and disable it. Your computer will ask you to restart and you will want to do that.

Everything works fine now.

SOURCE: Wacom pen not working - on the pen side

check the battery of the pen

SOURCE: My Wacom Intuos3 tablet won't switch into pen mode

The winning answer came courtesy of Mr Benedikt Schmitt of Wacom Europe, who offered the following solution: from the Windows Device Manager, disable the “Wacom Virtual Hid Driver” device. (Go to Control Panel > System and Maintenance > Device Manager, find the driver, right-click it and choose “Disable”.) One reboot later (welcome to Windows-land, circa 2008?), everything works as desired. Pressure and tilt sensitivity inside Photoshop still work, and the pen functions just fine in the rest of the Windows desktop. The absolute mapping makes it an absolute pleasure to point quickly and precisely. It makes my laser mouse feel rather clumsy navigating a large 24′ screen!

SOURCE: Wacom Tablet...PEN not WORKING!!!!

To make the 1st solution even easier, disconnect the tablet from the usb port, lay the pen flat on the tablet surface and plug the tablet back in. Worked like a charm for me.

SOURCE: My Tablet pen wont release, it acts like im clicking and holding

I'm just gonna pass on a email from Tech Support I recieved. 

"It sounds as though your pen has pressure in proximity. This is present when the tip sensor of your pen is stuck down causing the pen to think that it’s clicking before it’s even touching anything. What you may want to try would be to remove the nib from the tip end of the pen, it pulls straight out with a pair or tweezers or your teeth, and leave that out overnight with the pen left on its side. Place the nib back in the morning and if the issue persists then you may have a defective pen tip."

The rest consists of personal info and warranty advice so I'll leave it there.