If you're using the 2.5.0-Beta2 software (2.5-05), the IMU is not turned on by default. Look in the Arduino AConfig.h file, and change the entry for "Has_MPU9150" to 1, and change the entry for "Has_5803_14BA" to 1. Then reload the Arduino software. This will enable the IMU and the depth sensor.
I don't know if they are turned on by default in the Beta-3 software.