I am editing on a 2010 Macbook Pro with 8GB RAM. Recently, and seemingly for no reason, my log and transfer speed on AVCHD has gone from faster than real time to maybe 10x real time. I was on Snow Leopard, so I reimaged my hard drive and installed Mountain Lion, reinstalled FCP Studio, and yet the problem persists. Any ideas?
Did you resolve this? I have EXACTLY the same problem. Flying at normal pace for the first 5 mins (according to Activity Monitor, using 350% of the CPU). Then all of a sudden, it drops to 35% of CPU (about 5 mins into the transfer).