If I'm not mistaken, the Mechwarrior 4 website has the lastest game updates available for download. Better do a better job of searching next time .Official Mechwarrior 4 Site
Looks to me like your card is hot. Overclocked to a level where your getting those errors, happens to me when I OC, happens to everyone. Card could have came oc'ed like that or the card for some reason if not oc'ed can't take the default speeds in your system. You could get rivatuner and maybe down clock it a bit see if it helps, then again it could be like they say, a driver issue. The latest should be candy and work fine. Your case hot? Throw some fans in there or leave the case side off keep it cool. See if it does anything.