[Shaun]

First of all check the Salesforce Logs and find if there are any login attempts. If there are then there may be a problem with login id and password.

Next check the you network connections. If you are using a corporate firewall, as most companies use nowadays, then you may need to experiment with your network settings.

First try Native settings in the Eclipse. If that works then great else try a more brute force process. Change the Active Provider to manual, edit the proxy information for HTTP and HTTPS to include your corporate proxy IP, port, and network login.

If that also does not work then it would require a more thorough analysis. Maybe you installed a wrong JRE or something was corrupted. Also maybe network settings are not right, so also have a discussion with your network guys. 🙂