Übersicht
When updating WordPress from 4.1 to 4.1.1, after inputting FTP information, WordPress returns a blank page.
Ursache
WordPress 4.1 is shipped with a bug in its update module that prevents sending version information when looking for an available update through WordPress’ servers. (cf. ticket #31378)
Lösung
WordPress has included, temporarily, a second Update Now button. This button includes version information necessary to update WordPress. Click the second Update Now button.
WordPress 4.1 -> 4.1.1 bug workaround