Turn your security off on the router and see if you can connect then to eliminate any possible password issues. If you can connect then you're mistyping the password. If you still can't connect then try resetting the router to factory settings (unplugging and holding down the power button is the typical method). Keep in mind that if you've changed any settings on the router that you'll probably have to change all default passwords on all things that connect to the router. If a reset of the router doesn't work then there's probably some compatibility issues with your Thunderbolt and your router.
Also this link may offer some more troubleshooting steps. http://community.htc.com/na/htc-forums/android/f/107/p/13868/61694.aspx
Oh and it's "backwards" not "backwords"