sorry for the delay.
after that day my iMac crashed two times, and it seems that iTunes is not the reason of the crash. cause when it is "about to crash", my iMac just acts wierd. like DTerm (another cool app from app store) cannot work correctly. or some program (safari, finder, even, gcc seems to be unstable at the time) runs laggy than usual.
I think I might just figured out the reason, it possibly be third party software issue. I was using an app called "pps" which could be downloaded from app store.
anyway, after i removed the app, everything seems perfect!
and it is not tempurature issue... i think. cause that happenes randomly.
hope this comment does help to someone