toshiba problem, strange

sometimes my toshiba satellite refuses to cooperate on the keyboard, and types out 11111111111111111111 instead when i type words

i have tried anti-virus, then total re-install of xp, then substituting with an external u***** keyboard - could not solve the problem

this one is about 2 year old. Well, i will not buy toshiba again, but before i trash it, what is the bloody problem?