http://www.noaanews.noaa.gov/stories2007/s2831.htm
"In December, we found the effect on GPS receivers were more profound and wide spread than we expected," said Paul Kintner, Ph.D., professor of electrical and computer engineering at Cornell University. "Now we are concerned more severe consequences will occur during the next solar maximum."
"This solar radio burst occurred during the solar minimum, yet produced as much as 10 times more radio noise than the previous record," said Dale Gary, Ph.D., chair and professor of the physics department at New Jersey Institute of Technology. "Measurements with NJIT's solar radiotelescope confirmed, at its peak, the burst produced 20,000 times more radio emission than the entire rest of the sun. This was enough to swamp GPS receivers over the entire sunlit side of Earth."