I could not replicate the crash using the files attached:
https://www.dropbox.com/s/0mxffnfwlcwuicf/bst_openmeeg_meg.zip?dl=0
I just hacked some MEG sensor locations to complete the computation.
Can it be a pb with brainstorm MEG leadfield? or maybe it's because you did not provide the MEG sensor locations?
Alex