After installing otrs on CentOS 5, I can login with default user but I get this error when I try to make a new user:

can't resolve "localhost" to address at /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi/Net/DNS/Resolver/Base.pm line 750.

localhost is in the hosts file.  This machine is also a mailserver with postfix, a pop server, a caching nameserver and other stuff running.  The otrs database setup went fine.  I know that localhost is resolvable and I don't see other issues with this box. 

Any ideas what the problem could be or suggestions for troubleshooting?