[CentOS] nfs (v3?) fails to allow writes and permission changes

Hi All,
I have an nfs mount from my CentOS 5.3 client to a CentOS5.3 server. 
This has been functioning correctly for some years.
Beginning last week I had problems saving OpenOffice documents onto the 
nfs mounted volume.
OpenOffice just times out with a file io error.
So I tried just a simple shell - cd to the mounted volume did a vi 
create of text file - no problems.
tried a chmod +w on an owned file - returned okay but no change to the 
permissions when checked with ls -l
tried sudo chmod +w on the same file and get
[rkampen at robsws p_494]$ sudo chmod +w 5887_cover.pdf
Password:
chmod: changing permissions of `5887_cover.pdf': Operation not permitted
yet using gnome file browser I can change permissions on these nfs 
mounted files just fine - go figure.

This did work in the past - so what has changed?
how do I check what version of nfs is actually working?

 [rkampen at robsws p_494]$ mount
192.168.230.230:/NDG on /NDG type nfs (rw,noatime,intr,addr=192.168.230.230)

Any thoughts?
Thanks
Rob
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