laptop keyboard problem

[phalsedoom]

i got a dell latitude xpi 150. it has this annoying problem. occasionally certain keys will not work when I depress them. it is always the same keys too. "i" "u" "7" and "8" this does not ocurr immediately or every time. it is a transient problem. i swithed keyboards and the other keyboard did the exact same thing. it works fine when i use an external keyboard with it, but i wouls like to find out why this occurs. Any suggestions would be helpful.