Is this stock, rooted, rom flashed ect? We need to know more.
If its stock just do your through finger salute to boot into recovery (volume down, camera and power). Hold those three buttons while your booting your phone. If your stock you should still be able to root your phone. You might be able to wipe your caches and stuff but i don't know because i never actually used the stock recovery
If your rooted with no rom. Boot into recovery also and you should have a modified recover. Hopefully your up dated to cwm 5.0.2.7 or whatever. clear your cache dalvik cache (under advanced) and do a factory reset.
If you put a custom rom on there, sounds like the file somehow got corrupted. Follow the steps for a just rooted phone AND reflash your rom. You might have to use a different rom. If that didn't help post again.