MPU6050 strange behaviour

Dear InvenSense and MPU6050 users,

I'm using the MPU6050 by accessing the registers directly and reading the raw sensor data. But the MPU6050 doesn't behave as expected:
- Changing either accelerometer sensitivity or gyro sensitivity has no effect.
- The z axes of the accelerometer always reads 0x7fff

To illustrate the sensor signals you can find here some plots: http://www.scribd.com/doc/72231733/mpu6050

Is there a special initialization sequence to follow or is there another possibility to solve the problem?

Best regards,
Marc