Thanks for the link! The sip file seems to be for 64 bit, so no good for me as long as we run 32 bit.
Installing a version of of pyqt that was compiled against QT 4.5.3 was the ticket (in MotionBuilder anyway).
This is the installer I used: PyQwt plots data with Numerical Python and PyQt
An extension of QT, but it seems to work… 