FCP quits when capture prores 422 firewire

first off i read the article by chris how to capture using a firewire.........I have a few HDV tapes and i am trying to capture it into FCP2 using a firewire Proress 422 1080i 29.97 HQ. I start the capture and it starts working but a few minutes in FCP closes with no warning and it doesn't make a clip for what it captured. if i capture a short clip it works no problem but i have a few hours worth of video and i want to capture atleast an hour or 30 min at a time ......
I am using a mac pro 8gb ram i have plenty of room on my hard drive to capture....i tred using my local hard drive and capture to my raid and same problem....