Whitescreen after version 4

After running wordpress for 10 years, I’ve been spoiled by automated database backups, one-button-version-upgrades, and less and less payed attention to the technical details of being a wordpress webmaster.

Now I’m stuck and confused after not keeping track, and something has gone all wrong:

I have the symptoms google calls WSOD: white screen of death. This happens in the root, and the three main folders and all files in them, except the /wp-admin/upgrade.php that tells me: “No Update Required Your WordPress database is already up-to-date!”

I have deleted all my files in my /blog/ folder (after backing it up), uploaded fresh 4.1.1 files, and carefully transferred config-settings (I also added security salt – thank you wordpress security people!). As my wsod was already in place before I took action, I reset the active_plugins to a:0:{} though phpmyadmin. All old themes are gone.

My .htaccess file does not seem to make any difference (I checked that it looks right, and also deleted and recreated it), file permissions looks right (I think).

I’ve been through the detailed upgrade guide, and believe I have done all I should.

I still have white screens everywhere (except upgrade.php, and when I tried to echo out a hello world in my root index.php and that works). I am hosted at one.com (and have for many years without problems).

Now I’m out of ideas: what clues have I overlooked, how do I revive my http://stavelin.com/blog ?