Remove battery -- wait 5 minutes -- insert battery -- wait for reboot (may have to hold top button until red light shows).
Otherwise, place on known good wall charger for at least 2 hours before trying anything.
Occam's Razor nearly always applies when troubleshooting technology issues!
If anyone has been helpful to you, please show your appreciation by clicking the button inside of their post. Please click here and read, along with the threads to which it links, for helpful information to guide you as you proceed. I always recommend that you treat your BlackBerry like any other computing device, including using a regular backup schedule...click here for an article with instructions.