Wrong tempo when moving session to another computer

Hi,
I’ve been happily using ardour 2.0.5 on my Gentoo PPC box at home for quite a long time; when I needed to record some drums and voice in my sessions, I set up a P4 laptop with Xubuntu/Medibuntu/Pollycoke in order to bring it to the studio.
The problem is when I open the sessions on the notebook, waveforms are messed up (which I can solve applying stretch/shrink region) and -worst of all- the audio files tempo is slower compared to the Gentoo desktop.
The click actually beats the supposed tempos along the session, but the tracks (both recorded guitars and exported hydrogen drum machine) simply don’t match, which obviously makes useless recording new drums/voice tracks…
Any clues?

M.

the sample rate that you are running JACK at on each machine is different. make them the same. nothing more to it.