Christina-
Did you ever solve your Matrox codec issue?
I haven’t had to use the Matrox codec in a while, but several of my animations from years back used it.
Today when I tried to import some of the old Matrox MOVs, I got the same error you did.
Also tried reinstalling the 2018 Matrox VFW codec, but nothing changed.
-Steve Collier