Cannot connect to some hosts using tramp

[Angus Comber]

I have a number of unix hosts which I need to connect to which are all
located within our company LAN.

Some hosts I can connect to, others I can't for some reason.

I am using emacs 23.3.1.

I connect like this:

m-x tramp to get started (without this I find it doesn't work for ANY host).

c-x c-f //host:file

Then prompted for a password.

It works for a solaris box here but not a red hat linux host.

Any ideas why this might not be working?  Any config I can do to help?