Unable to sync applications due to authorization error

this is eitherbab iTunes or an iPhone error. My iPhone cannot sync it's apps or any in my library. iTunes tells me that I need to authorize my computer in order to sync or else it will delete my apps. I authorize my computer again and again and it gives the same messge :"including this computer you have successfully authorize one of five". But when I sync my phone the error remains the same. I'd like to keepmy apps and I'd also like to sync my phone so this needs to be fixed.