Package nfs-utils-1.2.2-7.el6 included with SL6 suffers from the problem described in RedHat Bugzilla #652786. That bug was reported for Fedora 14, but it appears to also affect Fedora 13 and SL6. I am unable to verify whether upstream has issued a fix for RHEL6. I manually applied the fix described in the bug report and tested that it works in SL6.
https://bugzilla.redhat.com/show_bug.cgi?id=652786
