page for setting up the Steam Client on the RNX-EasyN4:
The RNX-EasyN4 will not allow you to forward enough ports, to run Steam Client. You should try using the DMZ portion of this router if it is available. Alternatively you can try switching the router to bridged mode. You will need to contact your ISP to switch to bridged mode, so they can make the required changed on their end.
WTF? I think I remember reading on Steam's website that it won't work with a DMZ (they've currently got the support site shut down due to high volume, so I can't post a link). I also don't know anything about "bridged mode." Should I really try that?
After investigating a bit more on my computer (where Steam will load up), I've realized that it's not fully functional. I can get into a game and download an update for a game, but my Friends list won't load. It says there's no connection. I don't know if this could be related to the Steam Support page also being down or if it really is related to the issue with the other computer being unable to even log in. Sigh.