Backing up and connection to update server and itunes store

I am currently using the latest version of iTunes at Windows 7 and have the following problems:

i) I tried to sync my iphone 5s and it stops at step 2 of 7 (backing up) before proceeding further

ii) I am unable to access iTunes Store and received an error message stating that "make sure your network connection is active and try again"

ii) I am unable to check for updates and received an error message stating that "the software update server cannot be contacted and check whether your network connection is active".

I have no problems connecting to the internet and have passed all the tests when I run the Diagnostics .

Please help! Thanks.