You shouldnt enter anything else on that 8889 unless they made contributions outside of payroll.

Since youve fiddled around with it so much, what I would do now, is delete that Code W on the W2 and see if the 8889 disappears, if it doesnt then youve made some kind of entry on it, Delete that 8889.  Once its gone, then start over, enter the W on the W2, then go to the 8889 and click the Self or Family box on Line 1 then again in the Smart Worksheet below Line 2 and see if the error clears.