mtprint can not be used on Windows 7 (64bit) if the Miktex 2.9.4521 Version is used. It did not matter wether the Miktex 32-bit or the Miktex 64-bit version were used.
The bug could be reproduced on a system with Windows 7 Home Premium and on Windows 7 Prof., both were 64-bit instalations.
mtprint --verion oder mtprint --help resulted in "unexcpected condition", while other miktex programms did work
After uninstalling the new Miktex Version 2.9.4521 and installing Miktex 2.9.3972, mtprint did work again.