This is the most common "brick." You turn on the phone, and all you see is a white screen with a battery icon and a USB icon, or a black screen with a 507 error code. This means the OS has been erased, but no new OS is present.
The Bold 9900 had a notorious issue with . Over time, as you installed and uninstalled apps, the internal memory would develop "bad blocks." A standard factory reset doesn't fix these—it just hides them. Blackberry Bold 9900 Autoloader