John, this tilting of the earth was obviously caused by a magnetic anomaly. How long did it take for the instruments to recover? Did you have to tilt the plane to the right to maintain "level" flight? Did the engine quit? I would check the plane's tires for spurious surface cavitation (rubber and synthetic rubber don't stand up well to bursts of unbridled magnetism). Note: it's late and I'm tired (a pun?), so I might have left out an importatnt detail.
