Problem to interface TSL2561 with KL25Z and Motor Shield v3

Using Arduino Sensors
1

Hello, I'm a French student, so please excuse my English.
I am working on a robot with the KL25Z and the Arduino Motor Shield v3 and two motors 7.2V I also have some sensors like the SRF02 and the TSL2561, both of them are working with i2C.

TSL2561 is a digital light sensors which receive a value according to the light. https://www.sparkfun.com/products/12055

I have a problem with the TSL2561, it is working when my motors are off, I can receive the good value and a good precision but when I turned them on, after 5 - 10 sec they only receive the data "0". I looked the SDA and SCL channel with a logic analyser, and when the shutdown happend, there are no long things on SDA and SCL.

I have tried differents libraries, tried to unplug the others component and the TSL2561 still doesn't work when I turn on my motors.

My addresses are good, I solder the pullup jumper on one sensors, I tried to change the SDA and SCL pin with I2C_SCL,I2C_SDA to D7 and D8. But I have no clue about what is going on.

I'm using the USB to power the KL25Z and the batteries to power sensors and motors. I tried to powered sensors with USB, still not working.

I discovered that it happens only when my motors is running that the i2c is freezing. For instance if I block my wheel with my hand while my motors is turn on, it works (so it should not be a problem with the current) but if I drop the wheel for one second I can see on my logic analyser that there are nothing anymore on the SDA and SCL.
NB : When I do the same with the SRF02 which is also a component working with i2c, I haven't this problem.
Do you think the problem is coming from the shield or from the two motors ?
Do you think it could be a problem due to a noise of the motors ? And if it is, how can I solve this problem ?

KL25Z : http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=FRDM-KL25Z
Arduino Motor shield V3 : http://www.arduino.cc/en/Main/ArduinoMotorShieldR3
TSL2561 : https://www.sparkfun.com/products/12055

Please feel free to comment, share your opinions and propose solutions.

Thank you.

2

Update : I've just tried to replace my sensors with the isl29125, and I've exacty the same problem. I think the probem is not coming from the sensors but from the Arduino shield of from the motors.
Please help me I'm getting clueless about how I can fix it.

Thanks you