Does the second W-2 say "Corrected" on it? Sounds like your employer recalculated your Medicare tax withholding and updated your W-2. Enter the first W-2 as you normally would, then enter the box 5 and box 6 amounts (replacing those old figures). Be sure to keep both of your W-2s with the rest of your tax records.
You might want to contact your employer to verify which box 5 & box 6 are for the correct amounts.
