I'm glad your arduino bit fix was easy! Don't you love it when it's a simple solution?
There is a simple mod you can do to the bit (it was designed so you could make the modification by the bit's designers) that makes it so you can power it from the USB cable. If you are an intensive arduino user, you might want to consider doing this. It does take a little bit of soldering skill.
Look here: http://discuss.littlebits.cc/t/cant-get-the-usb-port-to-show-on-my-mac/21381/4
From my experimentation, you can use this method safely, even when a power bit is also attached to the Arduino (or other connected bits.) In fact, I often put an unpowered usb power on input bits, because that causes them to work properly.