AutoCAD 2012 'no internet connection'

Starting AutoCAD 2012, the Autodesk Exchange screen stays white and leads to the following error-messages: 'no internet connection'. But there is a connection. 'Autodesk server temporarily out of reach. Also not true because a colleague in another firm doesn't have the problem at the same moment. 'Your proxy is blocking Autodesk Exchange, contact your network administrator'. The Online Help isn't working either. See if you can install the cad manager tools from the dvd, and disable exchange. the in Options, set cad to NOT use online help. If you really need to use exchange or online help, you've got a browser that can get there.