Same with me, I am using Openshot 1.4.0 I get the following error too:
Failed to import 'from openshot import main'
I reinstalled gstreamer and mlt, nothing fixes it.
If you want to see what it looks like you can see the results here: http://www.youtube.com/watch?v=bTRWhoR_wOA
This is unacceptable.
The OP mentioned that the same thing happens in KDEnlive which is also based on MLT.
I believe that might be where the problem is: http://mltframework.org/twiki/bin/view/MLT/Projects