Factory reset via hboot.
To get there, pull the battery on your phone. When you turn it back on, hold power and volume down. Hold it until you get a white screen that says bunch of crap on the top about radio and version and what not. In the middle you'll have the option to select bootloader. In this screen you use the volume keys to move up and down, and the power button to select. Bootloader is the first option, so just hitting power should work. The next screen is the hboot screen. volume down and select factory reset, hit the power button, profit.
This will wipe your phone, so only do it if you really really can't get into your phone. And you probably should backup your internal (if you can) and external sd cards first.
Don't forget to put your battery cover back on, you won't get a signal without it on.