eh i'm here today mah, posted a few places.

can find me in quite a few places wan.
no ler. it's not the OS kicking in.
the OS when you on, it only gives some high frequency sound. that's it.
the KREK part it happens to mine only once a while. in fact, i don't even know how to make it go KREK.
i used the 18-200 to snap MANY photos already, paintball outing alone donno how many hundred shots, running around balblablaba - don't even here that KREK.
in my use so far only heard is say.......erm. 3 times? really donno how to re-create it. what i notice is when i point it downwards or slanted angle but it doesn't happen all the time, in fact rarely.
perhaps the OS device friction on something. not sure.
damn nice price.
but with your question - how often does your KREK happen?
the KREK sound (based on your desciption, here and via PM) it should be sounding like scratching a pen on a wall a bit.
IF it happens often, i think maybe that's why RM 1.2k cos i think RM 1.2k is really damn low for a lens like this. that's like 33% off.
judging by what you mentioned, i think it happens SO OFTEN. or else you wouldn't be asking. mine has taken a few thousand shots now and I've been using it frequently for past 3 months or so and i couldn't even remember when was the last i heard it.
erm...the krek only appeare when the os switch is on, if off no sound coming, the sound only came once in a while, when i'm in focus mode half press and after taking the photo...weird huh!