Using the kernel from linux-image-3.12-0.bpo.1-amd64 from wheezy-backports solves this problem. Now the nfsroot can be mounted via NFS v4 without any problems.
-- regards Thomas -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org