According to a article today at Digitimes, some sources are indicating that Nvidia will plan to launch their new MCP 78 chipset in just a few months. This will be Nvidia's next platform that includes integrated graphics, something they are relatively new in the market for.
Due to production issues, MCP 68 was delayed to market. AMD is planning to launch their next gen chipset before too long, which may make Nvidia fearful that vendors will turn to an AMD CPU, AMD chipset platform, rather than sticking with an AMD cpu and an Nvidia chipset.
AMD's 780 series platform isn't expected until mid 2008, so Nvidia has ample time to prepare. There is not yet an official press release from Nvidia regarding the launch of MCP 78.