I remember that the Silhouette export wasn't entirely clean (the resulting Nuke syntax had a few errors). This would probably cause the crashes especially if you would try to modify the splines in Nuke.
It would be great to get the Silhouette guys to fix this on their end.
I was going to do some tests with this but don't have time at the moment.
One thing I seem to remember was that the last keyframe in each Bezier was doubled up but I can't remember the other problems we saw.
Definitely let them know and lets hope they fix it!