Silverlight on client only works as local admin

I have client who has installed our Silverlight app. The app works fine when running from the IIS server. It also works from a client ma开发者_StackOverflow社区chine - but only if the user is logged in as local admin. If they log in with a non-admin account, they get a blank screen where the silverlight app should be.

When I look in the server logs I see that the XAP is being blocked, getting 401 response code.

Any suggestions? It feels like this has to do with accounts, which I am no expert in.

There is probably something wrong in the IIS security settings.

Is Anonymous authentication activated in IIS?