Probably asking the obvious but is the service actually running? Check in the Windows Startup button, Run, Services.msc and make sure that all services that start with "QlikView" are up and running. In addition to this, if you just have installed the server, you will need to reboot your computer so the permissions and users created during the install are working fine.
If you can get to the QEMC, check the Status tab, "Services" menu and all servers show the correct server name and "Running" status.
Christian, is the QlikView WebServer running as well? It may conflict with the IIS if both are listening to port 80 (check here), so the client might get an answer from the incorrect web server. Anyway, check this post and this thread regarding to your issue.