video playback double speed

mmm hoping someone can help here please, i posted earlier that i have a new
camcorder and have had difficulty getting it to work with fire wire where my
old one works perfect. Any way I tried a different port and it worked, so I
thought. Now when i record into movie maker and play back, all looks ok
then for about 1 second it speedsup,goes back to normalfor a few seconds and
speeds up again.... can any one offer any advice.. i guess my gut feeling
is i need a new firewire card.

thanks inadvance