While attempting to host a Team Fotress 2 (TF2) server on one of my home computers, I ran into the following error after installing the server files: "Unable to load Steam support library. This server will operate in LAN mode only."
After hours of looking on the internet, to no avail, I discovered the solution by accident. I happened to have the steam client (game client files) installed on the same computer, so I decided to attempt to connect to the server by playing the game locally. So I launched the steam client, and it said it was out of date. I ran the steam client update as prompted, then everything worked after that.
It seems that the hlds server utilizes the steam client libraries, and they have to both be latest revision. This only occurs when you attempt to install the steam server files on a computer that already has the steam client installed.
After this dilemma, I moved my TF2 server to an amazon EC2 instance. I followed the installation instructions verbatim, and it worked the first time without problems. I did get some warning messages regarding the inability to start the steam service, but it did not affect the TF2 server.
There you have it. I hope this helps someone!