As Noel commented, the issue seems to be fixed by the most recent kernel package:
$ uname -a Linux 2.6.28-4-server #6-Ubuntu SMP Thu Jan 1 23:42:42 UTC 2009 i686 GNU/Linux
Even when removing the suggested changes to /etc/defaults/nfs-common, the init script starts without problems.
As Noel commented, the issue seems to be fixed by the most recent kernel package:
$ uname -a
Linux 2.6.28-4-server #6-Ubuntu SMP Thu Jan 1 23:42:42 UTC 2009 i686 GNU/Linux
Even when removing the suggested changes to /etc/defaults/ nfs-common, the init script starts without problems.