Simply read this post and you issue will be solved.
issue: Load operation failed for query ‘GetAuthenticationInfo’. The remote server returned an error: NotFound.

1) This error is deceiving – the error doesn’t actually have to do with an incorrectly configured system.
2) The solution is simple

Login to your server (mine is Windows 2008 R2) > Open IIS Manager > select your Lightswitch site > click on Authentication (under IIS) > ensure ‘Anonymous Authentication’ is the only one enabled.

Restart your application from the browser and you should be good.  We’ll have more to come related to Lightswitch development.

UPDATED: 1/26/2012
If the above solutions does not work – just REPAIR .NET 4.0 and restart your server.  This just worked for me on a new server configuration.