Keyboards are pretty hardy bits of hardware, and usually last for quite a while. I think you either got unlucky, or something just went wrong somewhere.
You mentioned water damage as a tag, and I assume you have opened up the board. Apparently some people report washing out the membrane panels with water and a little detergent works may work - see elpin's comment there.
Most keyboards I have do seem to last quite a while, so its not new keyboards in general.
Finally, if your old keyboard still works and you want to do it, get an active USB -> PS/2 adaptor and use it with your system.