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 Windows 7 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.