I tried to upgrade Post-Plugin Library from 126.96.36.199 to 188.8.131.52 from the plugin management screen. The upgrade was successful, but the plugin wasn't reactivated.
Now I can't access the admin interface: I get blank pages. My blog works fine, though.
I tried to remove the files from the server and uploaded the 184.108.40.206 manually. Didn't work. I tried replacing the files with 220.127.116.11, which definitely worked. That didn't help either.