I would use SSH instead. Why? Because everytime I have asked or seen someone ask about rlogin, it generally goes off into using SSH instead for security reasons.

So I suggest trying that, depending on the linux you are trying to connect to, it may already have OpenSSH installed. If not, all the details are at the above site.

Now, for rlogin, if you STILL want to use it, check the ~/.rhosts file:

hostname username
Also make sure you port 513 is open.

I haven't used ProComm for rlogin/ssh before, so not sure how it works. I use OpenSSH client on Linux, and PuTTy on Windows.
I am a newbie, so I hope this is right. I am sure ppl will correct if not.