Itzik, I had the same model (KS639) -it never worked right, and died after about 20uses
the previous model KS638R works better but only takes 2GB cards
you liked so much was recorded with KS638 that I still use

I've tried many recorders, and concluded there is nothing better than stripped down old or new Canon digital camera, they can be as light as 55g and give excellent colors
I have chips to control digital cameras remotely so when it's time to land you just power off the camera (hide the lens) and don't risk breaking zoom lens

check this video
http://fmtv.us/rc/Delicate_Arch_Utah_.m4v
(open with QuickTime)
it was recorded off 400gram foam plane(Stryker) with Canon SD1000, . .
there was no place to land but drop dead onto rocks and dirt, I crashed few times and the camera survived every time because it takes one second to power off/hide lens.
More info:
http://www.rcgroups.com/forums/showthread.php?t=879965