I have been suffering with this problem too - after installing SP2 camcorder + PC just will NOT play!!!
Apparently IT IS a Microsoft issue - basically they have tightened up drivers to meet IEEE 1394 specs more closely - so drivers no longer recognise many devices as being FIREWIRE devices at all.
Anyway after trying many 'Fixes' to no avail - I found this set of instructions and BINGO my Panasonic NV-GX7 is working fine now - no problems at all!!
Hope this helps you and if you can spread the word (link) as there seems to be a lot of people struggling with this problem. Why Microshaft have not addressed this issue is totally beyond me, Christ! - they've had long enough to sort it!!!!

Code:
http://www.rme-audio.de/english/techinfo/fw800sp2.htm
Philter