I have a feeling that from Vista onwards LPT addresses followed a wider convention. Have you looked in your computer bios to see if an onboard LPT is enabled? If so you might want to disable it and try re-installing the card. 0x378 may then become available for your PP card.
First you could try setting Mach3 to EE000 or whatever value you have in the device properties. Mach3 uses LPT in a 'special' way.

Cheers,

Rob