I remember having the same problem with tcsh 6.05. When
I #undef'ed the following option in config_f.h and recompiled
tcsh it worked just fine:

/*
 * REMOTEHOST   Try to determine the remote host that we logged in from
 *              using first getpeername, and then the utmp file. If
 *              successful, set $REMOTEHOST to the name or address of the
 *              host
 */
#define REMOTEHOST

Hope this helps.

-- 
Blaz Zupan, Ljubljanska 19/b, 2000 Maribor, Slovenia
blaz.zupan@uni-mb.si, http://www.feri.uni-mb.si/~blaz/