You might try this page ...
http://www.nickengerer.org/personal-...eyboard-d00901
There are a set of reset points inside the Kindle (not available from the outside). Apparently you can short these with a small screwdriver. I'm not sure if this will fix it, but it might be worth a try.
(Picture from the article attached.)
If nothing works, you can usually find a Kindle Keyboard (in decent shape) for about $20 (including shipping) at shopgoodwill.com.