My guess is your GPU is driving your display too and somehow it has stalled. Or it could be that your GPU drew too much power and the system shutoff. Try setting the ExecutionEnvironment flag in the detect method to 'cpu' to see if that fixes things. If it does, then you can focus on figuring out why things stopped working on your GPU.
Information that could help is the output of gpuDevice, which tells you what mode your GPU is in.