I don't know if this is written somewhere, but it took me a while to troubleshoot.
I was having problems with my WiFi not being able to connect to my home network, I could see it just fine, however it would say Failure when I tried to connect and I would recieve "Input/Output Error".
So just in case someone runs into the same problem, for me, it turned out that it wouldn't connect because I didn't have a passphrase set for my home network. Silly thing but there you go, just in case someone is googling the problem and this might be the solution.
I'm using (or trying to use) a wireless network in my house. I tested Rasplex using a wired connection to the same computer, and it worked fine. When I switched to a wireless connection, it would not work. Yes, I've given it the password, and it says it is connected.
Boxee, using the same wireless connection and password, works fine. There's something here I do not understand.