Keyboard or computer or Vista problem

Regularly, my keyboard is producing incorrect punctuation and some letters.
question mark gives me É
forward slash gives é
apostrophe gives è
quotes gives È
occasionally the @ sign gives other signs.

Almost like it switches to French, spontaneously. I have to restart computer
to get it back to normal, but it is happening more often.
Any thought on what is causing this, and what I can do to correct it
(question mark)
Thanks.