Sharepoint 2010 - Access denied... even for farm admins

If you’re getting Access Denied for all users even after configured the Super User and Super Reader cache accounts…

I recently deployed a new site collection into a new content database. As soon as I tried to hit it, I got unexpected errors. I checked the logs which revealed the familiar stuff about the portalsuperuser and portalsuperreader accounts not being configured - object cache misses and so on, for example:

Object Cache: The super user account utilized by the cache is not configured. This can increase the number of cache misses, which causes the page requests to consume unneccesary system resources.

Fair enough, I thought. I had a quick look through… but to some surprise, everything was configured correctly. All looked absolutely normal.

I stepped through all the various points listed e.g., here, and everything checked out.

Still no dice.

The resolution? After a bit of head-scratching, I deleted and recreated the User Policy settings in Central Administration > Manage Web Applications - and boom, like that, all kicked back in to life.

Inexplicable. Hope this saves you some time!