Imovie no longer sees my cameras in 10.6.8 and yosemite.

I'm sure there are others out there with this issue. For a long period of time, my i Movie work well with my cameras, Canon Vixia HF20 and Sony vx1000 mini dv. Now nothing. I Movie won't even recognize my cameras nor will it open the thumbnail window. so, I upgraded from 10.6.8 to Yosemite. Things got worse. Now no Firewire recognition. Anyone have a clue?