Help needed to convert miniDvs onto iMac using iMovie '08

I have a JVC GR-DVL9500 camcorder and would like to import all my movies saved on miniDV onto my iMac using iMovie. Yet, it does not work even though I do the import manually using a proper firewire cable. I get a window to pop up on iMovie, the movie plays on my camcorder while it shows that data are being imported onto my iMac. Yet, no data are recorded in the folder created for this event in the library once the import done (all manually : I hit play on the camcorder and start importing on the iMovie screen). Any suggestion?