'Wacom warrants the product, to the original consumer purchaser, except for the Software and consumable items such as the pen nibs, to be free from defects in materials and workmanship under normal use and service for a period of one (1) year, from the date of original retail purchase, as evidenced by a copy of the receipt and registration with Wacom by mail or online within 30 days of purchase.'
Not going to do you any good now, but next time you need to go though Wacom instead of the store.
If you are SURE your software isn't the problem, and you have the correct drivers, and your computer is functioning properly, then check your usb ports and make sure they aren't burning out. They may work well enough to support a keyboard or mouse but not the tablet. I had issues with mine for a while until I got a powered USB hub, it would suddenly stop seeing it.