Which model of camcorder are you using?
What is your operating system? Does your operating system register the connection?
Are you able to capture video using the free download WinDV?
Does your operating system see the camera (check in devices)? If you're on Windows see if WinDV or Exsate DV Capture Live can see the camera (many, including myself, always use one of these in preference to PRE anyway).
Insanity is hereditary, you get it from your children
If this post or another user's post resolves the original issue, please mark the posts as correct and/or helpful accordingly. This helps other users with similar trouble get answers to their questions quicker. Thanks.
These are about Premiere Pro, but may help with troubleshooting Firewire problems
-and Windows http://forums.adobe.com/message/4708997