Microsoft admits WGA failures “coming up more commonly now” | Ed Bott’s Microsoft Report | ZDNet.com
For more info click on above link

Scrolling through the posts on Microsoft’s official WGA Validation Problems forum is like reading accident reports from a multiple-car pileup on Interstate 5. Many of the victims are completely innocent and have no idea what hit them, and cleaning up the mess can be a nightmare.

Even a casual reading of the posts at the WGA Validation Problems forum makes it clear that WGA has serious problems. But Microsoft refuses to share any hard data about WGA installations, making it impossible for independent observers to quantify the extent of the problems. Until now, that is.