First, try a battery pull. Or you could try a replacement battery (if your Bold's battery has been draining quickly, the battery could be going bad).

If all else fails, you may have to reload the operating system. I suggest going to CrackBerry and searching this topic. There is a tutorial on the site about restoring the OS on a nuked or bricked BlackBerry. This seems to be the solution in threads about a flashing LED and not powering on.

If you've been backing up your data periodically with BB Desktop Software, it'll be easy to restore all your settings and data. Keep in mind though, if you've saved photos and other files to internal memory instead of the external media card, you will lose those items during this process.