Cant verify media

Hello, whenever i start EF wich is totaly up to date and COH is running through steam after the litle loading i get tabbed down and when i tab back up it says : Cannot verify media. and i have to exit to windows. Any idea on how to solve this?

Did you usually play CoH without this problem?

Are you using your available bandwidth on another apps such as download managers, torrent clients, steam updates or similar?

Did you install a firewall recently?