I had the same problem. After upgrading to Froyo last weekend (using the registry hack), yesterday my phone wouldn't rotate anymore. I could only use it in landscape mode. Auto rotate was on, disabling and enabling it, did not help. Rebooting neither. The calibration tip, no solution. So, a factory reset it was. And hours of fun getting my phone back to where it was before... Just when the Android Market had a problem and downloading apps was a real pain in the ass... Let's hope this was a onetimer, or could this be one of the reasons Samsung withdraw it's Froyo release...?