can't capture HD clip

Now that I've finally ascertained that the firewire connection between the Canon HV20 and FCP is probably okay (see thread below), why can't I capture an HD clip from a marked in to out point? I've tried every imaginable combination of capture/firewire settings, yet I've only succeeded in capturing on the fly using Apple Intermediate Codec. If I use Firewire Basic, then try to capture the selected clip, the HV20's player haltingly jerks a few seconds on SLOW rewind, then stops dead... Can anyone relate?