Post archives link yields a 404 Not Found

I had the same problem: the template hierarchy is not serving up the right file from the hierarchy (at least it should serve index.php if there is no archive.php), but instead it gives a 404.

My solution is to go to the wp-admin interface, select settings>permalinks and change the common settings to some other permalink setting (I changed it from “post name” to “day and name”). Now try again and it should work. Afterwards you can change the settings back to where they were (in my case: “post name”) and it will still work, no 404.