Hi,
I think i've got something interesting about that.
I've got the same problem with my K5, here is a video with the same noise. I've send the original video file directly to youtube. And if i read the file with windows (XP pro 32bits) & VLC, the sound is here.
BUT,
When i watch it with my macbook, no more crack sounds !
So, i try to convert the video thru Quicktime, and now, i have a proper file than i can read on PC without that sound.
I'm sending it on youtube, so you can check by yourself.
Here is the video with the crack noise :
And here, the video converted on a Mac, without any crack sound :