I know this is an old topic, but one thing to consider...
I found a whitepaper on things that can cause the CM11A to lockup. Some have to do with attaching the serial cable incorrectly.
The whitepaper can be found on the old free software called heyu on their documentation page. I cannot post a link, but search for heyu.org, go to their documentation page, and click the CM11A_Reliability.txt link.
I personally have caused mine to lockup a couple of times. Recently, I think I ran into a type 4 lockup. Too bad too, as otherwise the CM11A is a pretty good device. I prefer serial ports over USB for stuff like this but I can't tell you why (maybe I am old fashioned, or maybe I am just old.)
Anyway, try unplugging the CM11A, removing the batteries for an hour, then attaching the serial cable before plugging in to the wall.
Good luck.
Mark.