Seems to be a problem related to running SSL – if I run SSL under Apache 2.2 or 2.4, WordPress breaks. WordPress itself seems to be causing the redirect, but where this is occurring is not clear. Maybe this is because WordPress does not use protocol-relative URL’s?
Hmm. WP works fine on my machine when I run Apache 2.2 with a somewhat different configuration instead of 2.4, maybe it’s an Apache problem.