We installed teamCity (5.0.2), and set up the build agents. After all of the settings correctly set up, we still couldn't see the buildAgent in the teamCity pages.
It turns out that the buildAgent.properties wasn't written properly - i.e. it appeared ok on the GUI when installing, but the file itself was written using escape characters, which prevented buildAgent attaching to teamCity server.
Solution was simple - just removed escape chars and it worked:
Hope this helps.
(this isn't a question, I just wanted to notify people if they came upon the same problem )