Disaster has struck nVidia recently, with a significant flaw in their as of yet unreleased 8800 GTX series. Due to a faulty resistor as a result of a manufacturing defect, many cards out of a particular batch are plagued with a resistor that will cause hard locks after a few hours of use. Scheduled for release in only two days, it couldn't have come at a worse time for the company. They seem resilient, however, and don't believe it will affect the launch date at all:

Clearly someone has made a mistake during the manufacturing process and NVIDIA is going to have to pull out all of the stops to meet its launch date. However, we are glad to see that NVIDIA is addressing these problems before the product gets into the hands of consumers.
The affected units are being recalled, few though there may be. If all goes as planned, the 8800 series will be available this week.