I have quite a few Arduinos lying around and only one has failed completely, which I think is because I "zapped" it with static electricity, which is a problem, as Chris Stratton suggested.
Make a habit of grounding yourself before handling electronics, for example by touching some metal (earthed) part before reaching for your Arduino. Don't work while standing on a synthetic carpet, for example.
but what causes my pin 5 to be dead?
- static electricity
- accidentally shorted an output pin to ground, which could damage the output driver if you are outputting HIGH
- accidentally connected an output pin to +5V, which could damage the output driver if you are outputting LOW
- connected the pin to a negative voltage
- connected the pin to more than +5V
- powering the board "parasitically" which means connecting power to the data pins before connecting power to the main power input
- tried to "sink or source" more than 40 mA which is the absolute maximum rating. For example, connecting an LED directly to the pin without a current-limiting resistor
The other link he refers to: Bad LCD? Bad microcontroller? Or what?