I am trying to create an image of docker, but docker stays forever while loading image layers:

I have tried this several times and it just stops loading at different points. I also tried docker-machine restart without any effect.
I am using a docker machine on Mac OS X:
$ docker -v Docker version 1.9.1, build a34a1d5 $ docker-machine -v docker-machine version 0.5.5, build 02c4254
Any idea how to fix this?
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