We have not verified if this is related to 64bit only but this has helped in the situation where the cameras appear to work but live video does not, in Win7 only.
1- Click the Start Button, type devmgmt.msc in the “Start Search” box and press Enter.
2- Expand the "IEEE 1394 Bus Host Controllers" node in the device tree on the right hand pane
3- Right click the host controller node select "Update driver software ..."
4- Select "Browse my computer for driver software"
5- Select "let me pick from a list of device driver on my computer ..." and Check the box before “Show compatible hardware”.
6. Choose the second option---1394 OHCI Compliant Host Controller (Legacy), and click next to update the driver.