To tell the truth, I never heard of anyone having a problem with wacom tablets, I have one and been using it for the past 4 years.. unless there is an obvious history of spilling something on it, like spilling a coke..
My Wacom tablet has buttons and touch controls that controls certain functions on the software (I never used Autodesk, I have Painter12).. furthermore, I can assign the buttons on my tablet for zooming or scrolling with the Wacom software that comes with tablet..
If your Wacom tablet (mine is different from yours) has such buttons and controls, open the Wacom software or its control panel (usually come with the Wacom tablet) and deactivate those buttons and controls that are responsible for zooming (to be safe, deactivate anything that has the word "scrolling" function).. hopefully, it would temporarily solve your zooming problem..
If that fails, you need to contact Wacom tech support for advice..
http://us.wacom.com/en/support
I have a similar problem but with a different button, the simplest way to explain it is as if someone is pressing the delete key, which is really annoying when typing a message or highlighting a picture..
After excluding ghosts and demons, I contacted Toshiba tech support (my laptop is Toshiba Seattleite A500).. and they told me to disconnect the tablet and the mouse and use the laptop without them for few days.. they also asked me to give them a little detail about my antivirus program I am using next time I contact them..
it turned up that after few days using the laptop without the mouse and the Wacom tablet, the delete keystroke started to play on its own..
The conclusion was that my keyboard was at fault, and they recommended to replace the keyboard immediately (they even have those DIY YouTube videos on replacing the keyboard on laptops)..
and they excluded a malware (a computer virus) because my antivirus is from a good brand Norton and with virus definitions upto date..
I advise you to change the controls on the tablet to cancel the zooming (and or scrolling function)function, if any.. if fail, disconnect the Wacom tablet from your computer completely and update your antivirus program, the Wacom driver, and the OS on you computer, if any are available..
If all fail, contact the Wacom and maybe the computer tech support for help..
All the best..