I had the same Problem, here's what to do.
Step 1) Use a small blade to remove the Cyber-Shot tab below the keyboard.
Step 2)Remove the rubber bit off, This will take the keyboard with it. Do this CAREFULLY and try not to remove the sticky glue-like substance.
Step 3) With Another blade slit the white cover on the top half, where the problem is and peel it back slightly CAREFULLY, if you remove it all it will be a nightmare putting it back on.
Step 4) Clean the effected Area With a Blade, Scratch off any dirt Lightly and try that.
Note: This may not work if this does not work it is likely your keyboard will need replacing.
I AM NOT RESPONSIBLE AND WILL NOT BE HELD RESPONSIBLE FOR ANY DAMAGE OR LOSS TO THE PHONE, IT'S CONTENTS OR FUNCTION IF THIS DOES NOT WORK EVEN IF THESE DETAILS CAUSED THE BREAKAGE OF YOUR PHONE. (Just Protecting Myself).
Hope this Works. :)
Ben Brown, August 2010
