xen 3.3 linux domU nfs locking failure?

[Harry Waddell <waddell%caravaninfotech.com@localhost>]

I've setup a bunch of linux PV domU's for a customer and they have been working
great, except that it appears that the guests can't do nfs locking. The 3 dom0
systems are amd64 arch running recent netbsd-5-1 branch kernels. A SLES8 HVM 
domU
I created can get lock, as can NetBSD and linux domUs running under XEN2. 

I'm not sure if this is a Xen 3 issue, a NetBSD issue, or something else 
entirely.
Has anyone experienced something similar or can anyone think of a way this 
could even be possible? 

Thanks, 

Harry Waddell