iMovie has not changed in how it imports video from camcorders to the best of my knowledge. Your DV camcorder with a Firewire connection should import to iM4, 5 (HD), or 6. So it would appear that there is a problem with a setting, hardware, or something else keeping it from working. Sooooo....
Let's explore your setup. You have a DV camcorder right? It has a Firewire port? You are connecting the camera, with a Firewire cable, directly to the Mac? Daisy chained off an external hard drive? Via a Firewire hub?
Does the menu of the camera feature different connection types that you can select from (e.g. Firewire, USB, A/V jacks, etc.)?
What mode do you put the camera in when you attempt to import? Camcorder record mode? VCR play mode? Other?
When you hook up the camera what exactly happens? Do you get absolutely nothing? Do you get a message that the camcorder is connected but then can not get it to import? Do you get an error message?
Are you in an iMovie project when you attempt to import? Or are you trying to see the camcorder from the desktop?
Are you SURE the cable you have is OK? Have you tried it on another device to verify? Some cables have the molded over plastic higher on the connector than others. I personally have had devices with deep ports on them that a cable with more molded plastic (less exposed metal) not connecting but swapping to another cable with less molding and more of the metal connector exposed working correctly.
Patrick