Look in "Release Notes for Mathcad 14", in the file \Mathcad\Mathcad 14\doc\relnotes.htm:
Problems fixed in Mathcad 14 M011
1426375
Enterprise users who upgrade from Mathcad 14.0 to Mathcad 14 M010, and call a function from any of the four Extension Packs get the error message "bad_assembly_name."
Then try to reinstall the upgrade M011, if not sucess, try to contact mathcad but now with this other information. Maybe with this catch their attention.
Regards. Alvaro.