MPU-9150 some accel and Gyro directions work some do not

I have two (2) MPU-9150 breakouts from Sparkfun and both of them exhibit the following behavior:

I use I2C to access registers: 0x3B through 0x48 (All Accels. and Gyros).
The following Accelerometer directions work: X
The following Gyro directions work: x z

Which means the following Accelerometer direction do not work: Y Z
and the following Gyro directions do not work: y

The ones that do not work produce all zeros.

I am using a PIC18 processor, and I could post my code, but it is weird how some work perfectly and some do not. I am accessing all the registers the same way and I have tried all sorts of different settings.

Can someone provide some insight?