I've been trying to look for a solution, and I found out that my system have 2 corrupted file :
/System/Library/Keychain/X509Anchors
/System/Library/Keychain/X509Certificates
and I have to replace those with 2 normal file on another machine
so if anyone can sign in to itunes music store normally, please send me those 2 files
my email is vernicex@yahoo.com
thanks for helping me !
p/s : sorry for my bad english