Can't Transfer Files

I'm trying to run an SFS server on a gentoo system running 2.6.9, with 
nfs-utils 1.0.6.  When connecting to it from a client, I am able to 
browse around the directories just fine, and read and write to files as 
long as they are very, very small.  However, as soon as I try to do 
anything with a decent sized file, sfs on the client computer will 
essentially freeze.  All sfs connections to anywhere will stop working. 
  Eventually, 15-45 min later, sfs will 'unfreeze', and if, say, I was 
copying the file, the first couple 100k would be copied.

It is not a problem, as far as I can tell, with the client - the client 
can connect to another sfs server I am running (gentoo 2.4.20, nfs-utils 
1.0.6) perfectly fine.  In addition, this occurs on every single client 
I have tested with this server.

I do not think it is a problem with NFS, as I can mount the NFS exports 
on the server and move files around at will without any problem.
There is no abnormal output to the logs by sfs or nfs on either the 
client or the server.

And yes, this is all the same version of SFS - from the cvs repository 
approx. end of August.

Comments, suggestions, solutions?

-MK