rlogin sometimes hangs (from FC6 client)

I have just moved to Fedora Core 6 on my desktop computer at work. We
have a mixed environment of Windows PCs a few Linux ones and a number
of Solaris target systems.

When I rlogin from my new FC6 system to the Solaris systems the login
sometimes just hangs, i.e. I type "rlogin crusade" and nothing happens
for several minutes then I get a timeout message.

This seems to happen only on the FC6 systems, I have tried it from one
other FC6 system and it's the same but from a kubuntu installation (on
the same sub-net) it doesn't happen.  The rlogin hangs maybe one time
in four or so, the other times it connects normally and works OK from
then on.
 
Does anyone have any ideas what might be causing this problem?

-- 
Chris Green