ITunes check for update error message

Hello,
When I click "Check for Update" in iTunes, then the following error shows.
I am linked to the net by system of an Ethernet Cable. Also I am able to contact the iTunes store, so defiantly I have a relation to the web in iTunes.
But now it says, try again later and I have been trying so many times. Is this a error with iTunes or Apple?
Error : the iPhone software update server could not be connected.
Make sure your network settings are correct and your network connection is active, or try again later.
Please help me.
Thanks a lot.
