I have the same problem and the 5.02 upgrade did not fix it on my Toshiba Qosimo. I installed a firewire PCI Express card into the laptop and disabled the firewire on the mother board and now it works just fine. Premiere CS5 is not the only software that has had a problem with that internal firewire port, but I would love for Adobe to take another crack at fixing it.
For the IEEE-1394a connector on the MoBo, check the driver in Win7. You want to make sure that it is set to the driver with "Legacy" in the name.
Something we have found is restarting the computer with the camera connected to the firewire and camera on in camera mode when the computer boots up, usually allows the computer to detect the firewire is connected.
Although i only have this issue with an old sony fx1, our hvr m15u decks work fine no matter how we connect them.