Update 5/30/17 - SMS Hangs Dash
Just worth a mention so everyone understands what may happen on their Dash when receiving messages:
Stored / unread / generally somehow-messed-up SMS messages can hang the Dash when running firmware 0.9.11. The source of the SMS's can be a failed / hung-up OTA attempt, or (in my case this weekend) my very own SMS sent to device that was not correctly processed. In other words, the Dash may hang if you've tried to send it an SMS, even if you have not tried to program it over-the-air.
The solution is the same in both cases: Load the Dash Pass-through sketch (from Arduino > File > Examples > Dash Examples). This gives direct access to the modem via AT commands, and you can read and delete the SMS's from there, which will free up your Dash to run normally again under 0.9.11.