Identification
"Bricking" commonly occurs when a user tries to use software to unlock the PSP to play downloaded games or software. Sometimes this software contains viruses that can block the normal functions of the PSP.
Effects
A bricked PSP will not display any picture even though the lights come on when it is powered up. In some cases of bricking, the battery will have to be removed to get it to turn off.
Prevention/Solution
The best way to avoid bricking is to stay away from any illegitimate or homebrew software. Thoroughly investigate anything that you may be installing. If the PSP becomes bricked legitimately, and it's under warranty, contact Sony about a possible replacement.