Did you have any software on CD-Rom with the camera? And if so, have you installed it on your computer? I found with my Panasonic camera that the video clips were not even recognised as being present on the SD card unless I installed (on my PC) the Panasonic program (gross MB of space!) that came with the camera.
Now i have a Mac laptop (and the same camera), I haven't had to install the Panasonic software, as the stills go into Iphoto and the video clips into Imovie with no bother.