HOT Sensor - any suggestions?

Currently, I have an uno hooked up to an ultrasonic distance sensor and an ardafruit motor shield (I will edit this and upload a wiring diagram soon). The ultrasonic distance sensor requires 5V, Ground, and two GPIO pins, I am choosing pins 7 and 8. The ardofruit motor shield requires the SCL, SDA, 5V, and ground pins to operate (as well as an independent power source). Note: I am not stacking the shield onto the board at the moment because I am doing prototyping and don't want to solder yet.
The problem is that whenever I connect the common ground to the motor shield, the processor chip on my distance sensor heats up very hot - why is this happening? I don't have any power going into the motor shield - its acting like when i connect the ground pin a lot of current is flowing through my distance sensor, which I don't understand why that would happen.

**Edit - Once I stack the shield on top of the uno everything works fine, its only when the shield is not stacked that the sensor heats up... odd

This happened to me with the DHT11, I had the wiring fine, I checked more than enough times, and it just melted. Litterally.

Must be a wiring error.

Post clear pictures of the setup.

Here is a breadboard view of my exact wiring

That's a Fritzing picture.
Regarded by the 'greybeards' here as almost useless.
What is should be and what it is could be completely different.
A common beginners 'mistake' is the use of a long breadboard with interrupted power rails.
Post a 'real' picture.

Check the voltage levels with your multimeter, to see whether you get the 0V and 5V levels where you expect them to be.

Those fritzings may be of use for you to figure out how to do the wiring, they're useless for anything else like showing what your wiring is, or as circuit diagram.