problems with ip_conntrack on Linux 2.6.x (x>5)

With Linux 2.6.6 or later, neither the SFS client nor the server is
usable when the ip_conntrack module is loaded.

The message is
ip_conntrack_in: Frag of proto 17 (hook=0)

and the NFS mount keeps hanging (with occasional short bursts of data
transfer).

If one uses Linux 2.6.5 with ip_conntrack, or later kernels without
ip_conntrack, SFS behaves fine.

Jaako Niemi has pointed out that a localhost NFS mount produces the same
effect.

I have tried to use 2.6.7's raw table and NOTRACK target, but I am
either usinng it incorrectly or it doesn't make a difference.

This threatens to make SFS nonviable for me.  Can anyone help?