Check your Language...pref panel and see what language you have selected. Don't remember exactly what that panel was called in Tiger, it's now called Language and Text. There is a tab called "Input Sources" and that should have "U.S." and probably "U.S. Extended" checked.
Do you have any software that 'rearranges' the output of any key? Make sure "Dvorak" is not selected in the above panel, even though I think you'd have massively different output with any version of that set up.
Can you try another keyboard on the machine, plug into the USB port? You may also need to 'fiddle' with the "Keyboard..." pref panel to be sure the Mac is using the other keyboard.
Lastly, it is not terribly difficult to remove/replace that keyboard, if I recall correctly. It shouldn't rut to remove it, check for any obvious abrasions, scratches on the bottom or signs of anything rubbing it, especially near those keys. You might as well check that its cable is secure, while you're at it.