I just learned from Dell (although the issue is over a year in the making) that there is a Critical BIOS update for the Latitude D6xx series including 610 620 630 laptops. It relates to the temperature management of the system. Apparently there is a serious (but intermittent) problem with the nVidia video adapters overheating, which eventually will damage the motherboard. The most recent BIOS update addresses this issue by keeping the system fan running at a higher speed, and a new algorithm to manage the heat within the system. Apparently, left untreated, they have seen a number of laptops need new motherboards, and client who are outside of warranty support may be stuck.