In all the years I've been editing miniDV tape (DV, DV widescreen and HDV), I have never had to change the setting on the camcorder. iMovie - and the firewire communications protocol have always taken care of that. Final Cut Express and Pro also take care of the video format being imported.
Granted, I use Sony DV/HDV camcorders, but they have taken tapes from Panasonics, Canons and JVCs in DV and HDV format and have not had any issue.
That said, I am on OSX 10.5.8 and running either (occasionally) iMovie '09 (v 8.0.5) and mostly Final Cut Express 4 (v 4.0.1), but I don't believe that *should* make much difference.
I was about to suggest you go to the Apple support area - but see that you have already posted the question.
I found a couple of other interesting posts there by searching "HV30" - relevant suggestions:
1) FileVault must be off.
2) Is the camcorder firewire connection directly into the Mac or is it connected to something else? It should be a direct connection.
3) Camcorder is also plugged into AC power (and obviously in "Play" mode - I know you know this, but i *had* to).
4) You do not have "Nikon Transfer" installed.
5) You re-installed iLife from the OSX system disc that came with the 'puter.
I'll keep reading and see if anything else looks useful...