|nVidia has released the response as seen in the link. Particularly interesting, however, is this part of the e-mail sent to certain nVidia employees ( this was not posted at the given link ):
We have been working very closely with Valve on the development of Half Life 2 and tuning for NVIDIA GPU's. And until a week ago had been in close contact with their technical team. It appears that, in preparation for ATI's Shader Days conference, they have misinterpreted bugs associated with a beta version of our release 50 driver.
You also may have heard that Valve has closed a multi-million dollar marketing deal with ATI. Valve invited us to bid on an exclusive marketing arrangement but we felt the price tag was far too high. We elected not to participate. We have no evidence or reason to believe that Valve's presentation yesterday was influenced by their marketing relationship with ATI.
Source : NFI