I have a Raspberry Pi (Model B) attached to a Roomba. I'm using this part to bring the unregulated 17V+ power of the Roomba down the 5V/1A of the Pi. The problem is that the Pi will randomly reboot and cause peripherals (such as the bluetooth adapter) to freak out and not work. We can sometimes drive it around for a little while before it reboots, other times it happens almost immediately.
The Raspberry Pi B, and in particular the Raspberry Pi B2 are fairly sensitive to having enough current to meet their peek power needs. For most of my apps, I have been using a 1.5A supply, and that has been more than sufficient for the Raspberry Pi B+, however when I started trying to use the Raspberry Pi B2 I needed a peak of 3A to be able to not have it "brown out" and reboot.
I would recommend upping your available power, and see if it makes a difference.