I am having exactly the same issues with regards to captured HD in cs3.
To hopefully shed some light here though, I am using PC (i7, 4GB) and I am capturing entire tapes at a time. So it’s probably not the Mac or the short clips being captured…
I have long suspected that it was an issue with my hard drive and have installed a system monitor (Moo0)…I can see the hard drive maxing out in the red while the project attempts to open but my processors and memory are basically idling while the hard drive is working red lining. As soon as the project is finally open, the HD idles too.
I would be very interested to find out if it because the 5400’s are not good enough…sounds like it to me!