Xp Midi Mate Trouble!, Problem with USB MIDI interface Options

[dissident]

I just bought a an "XP MIDI mate" USB MIDI interface, by Audiotrak, to use with my Roland FP-8 digital piano. When I plug it in the computer recognizes it right away and i can choose it in the MIDI-in and out menu in Cubase SX. The weird thing is that when I use for example LM4 or another VST instrument in Cubase and try to play on my piano, all the notes don't come through. I can see in the little MIDI-parameter, next to the midi chanel in cubase, that not all the notes I play are registered. When I play fast almost none of the notes I play are registered and only on ore tho notes are played by the VST instrument.

Does anyone know if this is a software problem, a problem caused by the midi interface or a problem with my digital piano?

thanks!