500 error when searching message InBox

I'm getting a 500 error when I conduct a search on the messages page in Vumi Go.

![screen shot 2014-02-13 at 12 38 22 pm](https://f.cloud.github.com/assets/1521387/2158928/ba94c9ae-949b-11e3-9735-4d09c92e6798.png)