MIDI playback out of sync ?

First time I'm trying a real MIDI (not soft-synth) with PT.

While the exact same IN/OUT plays perfectly in sync under Cubase, if I try the same setup under PT, the playback of my external module is completely out of sync...

Any idea why this would be ?

1) created a midi track
2) set IN to Axiom Port 1 (USB)
3) set OUT to a Roland XV-5080 sound module

I'm not drunk I play straight... But playback is delayed by about 1/2 note!...

And I used a Boom box on that project, which tells me I'm following the same midi clock...