It happens form time to time. Flying back across Sasketchewan last April in the 182, I flew for 1.4 hours with none of three GPS's (one VFR panel monuted, and two Garmin handhelds) able to get a fix. I could have really used the nav there, as it is rather featureless, and I was too low to receive a VOR in a meaninful way, for most of the trip!
Every now and again, the GPS system does not work for a while. It's still the best thing ever though!