Hi, welcome to the forum. For anyone to realy help with your problems you should give more details of your rig including drive setup Operating system, etc. But my best guess so far would that, you may be capturing to the system drive and that isn't going to be a real winner!
I ran bio updates, changed my performance settings memory and it has seemed to fix this issue.
I had a problem when I would try to export
to my dv deck. It would only show a single frame
and then it would say export finished after a few seconds. I
began digging around changing setting after setting. I
found the solution! Go to Project/Projectsettings/
video rendering and play back and change it to
Mercury play back engine software only. This fixed
it for me and I use this setting to export only. It took
all day for me to get it to work, but hopefully I can
save some heartache with this tip.