All of a sudden my trusty cineform software doesn't see my JVC HD100. It says
"no capture device found".

my vegas 6d also doesn't see the camera...

what are possible culprits?

Firewire card, or the camera itself (either the connector is damaged or a camera setting.) You have ruled out a particular piece of software as Vegas doesn't use CineForm tools for capturing. I good technique to fix a Window driver issue is to use Device Manager and uninstall your FireWire card's drivers then reboot. On the next restart the Firewire device will be reinstalled automatically, and so will the camera drivers now we you attach it. If you don't see the found new hardware message when you add the camera then the it is something on camera (menu setting or damaged port.)

As mentioned earlier, my computer stopped "Seeing" my camera and therefore couldn't capture. When I went to device manager, the fire wire card didn't even show up! The Fix: So I removed the firewire card physically, turned the computer on then of. Reinstalled the card and presto, the computer and camera were best friends again--they were talking to each other. Apparently drivers are already on XP for generic firewire cards.