Can I use F/W 400 and 800 at same time?

I'm trying to get a video editing set up. I just got a Western Digital 500gb Studio Edition HD. I'm putting my camera in the firewire 400 slot and the HD through the 800. However it seems to not be able to handle both. I'm editing in Final cut and trying to capture video. Its been capturing the small clips (10 seconds) fine but anything large (5+ mins) it keeps freezing up telling me either that frames were dropped or the camera lost connection.

Am I not able to run both at the same time? That would suck and seems stupid.

What are my options besides putting everything on my HD first then transferring?

Using MBP with OS X 10.4.11

You can use both at the same time! Which model of macbook pro is it? Differing models have different power allowances from the firewire sockets and on several models there is a maximum allowable (shared).

If you check the specs on Apple's site it will tell you. On the core2duo iMac for example you get 15watts between the FW400 and FW800, on the santa rosa you get 7 watts specifically for each one.