In order for RPM to correctly read and write to and from
NFS shres, it needs to be recompiled. The 2.2.x kernel and
the newest libraries have done away with the old file
locking routines. Any program compiled with the old flock
emulation (which has been now COMPLETELY replaced by real
BSD file locking) needs to be recompiled with the new
libraries in order to do locking correclty on NFS shares.
Without recompiling those programs, they will not be able
to lock on an NFS share and usually won't be able to read
or write from or to them.

I've had this problem with elm and sendmail and now rpm.
(I've also had it with non-RedHat stuff like cucipop and
the FrontPage Server Extensions) Everything I recompiled
works fine now, but before I did, it was quite frustrating.

Take a look in the Linux source tree:

linux/Documentation/locks.txt

for information about the new locking scheme.

This is very important that you release updates to all
programs that have this problem. Professional organizations
use NFS often. It's quite tedious if we have to try and
recompile everything that needs it. (Especially in cases
like sendmail, where compiling requires configuration in
order to produce the appropriate binary that has the same
support as the one installed with the RPM)