This weekend I tried placing my iPhone 4S in a blackberry 9900 leather holster to see how it fit. Now when I try to use the compass or any app that uses the compass I always get prompted to calibrate it and have to do the figure 8 pattern for 10 seconds. I can be in the middle of an open field and always have to do this. I did not have to before. I tried rebooting the phone and a restore and it didn't resolve the issue. I don't know of anyway to degauss the phone. Loks like I will have to exchange it.