wcf service hosted in mvc3 app with windows authentication fails on one machine but works on another

I have a wcf service hosted inside an MVC3 web application with windows authentication (anonymous disabled)..

On one machine when I call the svc file, I see the 2 requests return 401 then finally finally the response with status 200 (the challenge mechanism as it should be)

On another machine, I can see there is no challenge occuring, instead, the mvc account controller runs into an infinite loop ..

I use IISExpress and both are using the same web.config and applicationhost.config (config for iisexpress)... so something else must be 开发者_高级运维different on the failing machine, but I can't seem to figure out what it might be.

The website runs well on both machines.

I deleted the solution folder and checked it out from version control into a fresh folder. Now everything works again... must have been something in the folder (secruity settings?) that changed behaviour. Strange, don't know what caused it...