Actually they have their own physical interface. One is using the FW interface on the MB, the other is a plug in PCI-e card. We did run into this issue a long time ago when we first built the stations, when trying to run both cameras off of a single interface, but at that time I was able to cut the bandwidth in half and get them to work temporarily. We bought a seperate interface and cranked them both back up to 400mbps and haven't had a problem since (that was about 1.5 years ago). This problem seems much different, as I am unable to get either camera to snap even when lowering to the minimum selectable value of 100mbps in NI max. I can however finally get it to snap when lowering the resolution from the default format 7 resolution of 1632x1234 to 800x600 and lower.
Strange the registry tweak didn't work because the key described in the resolution did not exist, and I had to create. I thought that was going to fix it. I did make sure the controller numbers and interface numbers matched up when making the tweak. Seems like the problem in the MS knowledgebase is very close to what I am seeing, just the resoluiton doesn't seem to work in Vista 64.