My little 2300c came to me with a few dead keys. I took the keyboard apart and found that they were the last three on a single trace, and there was a dark spot just before the dead keys. I said to myself "Oh noes! Fizzled trace! I guess I need a new keyboard..."

In a fit of brilliance (they don't happen often), I carefully scribbled over the dead area with a pencil. Works great now. Graphite FTW!