I have not come across this error before, however I can tell you how we have this set up at our site, which has a number of Sun (Solaris 8) and HP/Compaq (Tru64) systems.
For rcp (and other r... commands) to work from the current system (Host-A) to a remote system (Host-B), set up the following:
On Host-B, the remote system, in the default login directory of the remote user create a .rhosts file (owned by the remote user, chmod 600) with the following entry:
Host-A.domain.com <username-on-A>
(Note Fully Qualified Domain Names seem to be required on Sun systems but are optional on HP/Compaq systems)
On Host-B, the remote system, in /etc/hosts add the entry:
<IP-Address-of-Host-A> Host-A.domain.com Host-A
In practice we have the same .rhosts on all systems, and each systems /etc/hosts file contains all our known systems, so that we can rcp from any system to any system.
I hope that helps.
Mike