NFS server fails to write files

[Patrick Wagstrom]

Hey everyone,

I'm having some strangeness going on with my NFS mount from my Ubuntu
(Warty) system to any other system.  Basically, I can create files using
the "touch" command, but I can't seem to add anything else to them.  

When I try editing a file in vim on the NFS mount here is the output
that I get upon trying to save:

"foo.txt" E667: Fsync failed
WARNING: Original file may be lost or damaged
don't quit the editor until the file is successfully written!

The 0 byte file is created, but it is not populated with any of the
data.  I've been trying to degenerate most simple case to try and debug
this.  Here's my /etc/exports file, the top export is the one I'm
working on right now, but it pesists with the other rw exports:

# /etc/exports: the access control list for filesystems which may be
exported
#               to NFS clients.  See exports(5).
/mnt/store 127.0.0.1(rw,insecure,no_root_squash,sync)
/mnt/store 192.168.10.3/255.255.255.0(rw,no_root_squash,sync)
/home/patrick 192.168.10.2(ro,async)
/ 192.168.10.3/255.255.255.0(ro,async)
/home 192.168.10.100(rw,sync)

When I'm on my NFS server and a I do a call to mount /mnt/store using
the command "mount -t nfs localhost:/mnt/store /mnt/tmp" it is
able to mount the filesystem okay.  I can touch files, and create new
zero byte files in /mnt/tmp, but I can't put anything in the files.
When I try running other commands that write to the filesystem, I get
errors like this:

patrick at dreams /mnt/tmp $ ls > foo.txt
ls: write error: Invalid argument

I know that I still have write access because I'm able to delete files
from the directory.  So I'm thinking this has something weird to do with
file syncing.  I've tried both the async and the sync options.  In
addition, I made sure that my iptables were empty so nothing is getting
blocked.

Read-only NFS works just fine.  It just would be nice to allow
read/write NFS.  Any gurus out there want to help me out?

Thanks,

Patrick Wagstrom