From the FAQ:

When I try to login, I get a '605 - Timeout' error. How do I fix this?
This error is very general. It means that the Powder Toy cannot communicate with the server, usually because there is no internet connection, or the port used (port 80) has been intentionally blocked by an administrator. If you're trying to use the Powder Toy from within a corporate or school network, it is likely you'll need to use a proxy. Another known cause is Firewall or internet filtering software that runs on the computer (e.g Windows Live Family Safety), if this is the case, the relevant proxy settings need to be acquired, or the software disabled.

It might be a firewall you have, or the network you are using is blocking it.