ok, my mistake. it may be that the.current version of gpe is n800 only. also you have to get extras. look at details of the failure message.
more simple go back to the maemo pages, on right hand, search gpe with the constraint IT2006 (below), you ll find gpe pim. same extras will be needed i guess. don't hesitate to visit developper's page linked to download them before. advice :
reading the how to pages willl help A LOT!