From the "What is Gnutella?" page:

"There is no official program named "Gnutella". The original version, 0.56, was released as an early beta. The program was excellent, but not completed. This version contained defects that contribute to poor functioning of the network, which consists of all the computers running a client on the Internet at the same time. All existing robust clients are clones, with their functionality derived from a reverse engineering effort on the original program. The proliferation of the old software has prevented the Gnutella network from reaching its full potentials."

So in other words, yes, you should download a newer client.