I just found this thread so I missed it last year.
I can’t believe someone would suggest to a user to use Motionbuilder.
The program is great yes but it costs at least as much as Softimage!
Why then have motor? The guy was asking how to fix the problem. This sort of thinking is just what Autodesk wants. Buy buy more software. :/
If you can’t contribute to helping others solve the problems then don’t suggest they go out and spend another 4 thousand dollars on a new piece of software.
At any rate this bug is serious. The software should not crash the system. It should gracefully quit. Suggesting that someone solve an issue by spending more money is just bad. :/ I do not have any imput to help but I was looking for information on how to use motor as there is not much in the docs about it other than basic setups.
Digital Tutors and a few others have nice tuts. I shall look there if not here.

Hello,

I ran into the same problem as the OP.
For the benefit of others who find this thread like I did…

The mistake I was making to cause the crash as described by the OP, is an attempt to use the tag template defined for the user rig as the tag template for the mocap rig.

You need to create two different tag templates.
1) User Rig
2) Mocap Rig

When you choose: Animate>MOTOR>MocapToRig ... it asks you to select a Mocap Rig Tag Template (NOT the User Rig Tag template).

Remember to Apply your tag templates, as well!

Good luck, I hope this helps someone :)