Four very intense X class solar flares originated from active sunspot region 10930 on December 5, 6, 13, and 14 of 2006. The solar radio bursts associated with the solar flares on December 6, 13, and 14 radiated enough microwave power and with the proper polarization to cause severe fading of the GPS carrier signals. During these events, each lasting up to an hour, nearly identical patterns of intermittent signal fading were observed along all GPS satellite links from receivers located on the sunlit side of Earth (even from receivers separated by thousands of miles). The depth of these GPS signal fades were modulated by the local solar incidence angle (due to the anisotropy of the GPS antenna gain). The solar radio burst on December 6 was particularly intense and caused GPS signal fades in excess of 25 dB, intermittent loss of lock on several GPS satellites, and outage periods with complete loss of GPS positioning information lasting for several minutes. Peak GPS positioning errors in the horizontal and vertical directions during the event reached approximately 20 and 60 meters, respectively. While deep signal fading of the GPS carrier signals were observed during the solar radio bursts on December 6, 13 and 14, only the December 6 solar radio burst was strong enough to substantially impact GPS tracking and positioning accuracy.