FreeBSD 5.3-RC1 loopback filesystem + quota hangups

Any process attempting to access loopback filesystem created with dd
if=/dev/zero, configured with mdconfig -a -t vnode -f file,
initialized with newfs, and mounted with the userquota option on
FreeBSD 5.3-RC1 hangs in the D state.

Hand specifying a userquota=/anywhere/outside/the/loopback/filesystem
however, seems to work fine.  Is there any way to allow the default
quota.user and quota.group to be located in the root directory of the
loopback filesystem itself without experiencing these D state hangups?

Tony Arcieri