Contributions are gifts for purposes of the gift tax. Back then, you had a $13K gift tax annual exclusion. Your $43,000 contribution to the 529 created a taxable gift of $30,000 (or more, if you made any other gifts to your son during the year). You owe a late gift tax return to the IRS. But if you make the 5 year election on that form, your gift is reduced to only $5,600 and you likely do not have a taxable gift.
You can do the same thing for the 2011 contribution of $20,000. The 5 year election brings the gift down to $4,000. Your total gifts would be the $4,000 plus another $5,600 from the 2010 election, or $9,600 in total for 2011.
If you are married, the gift splitting election could be made to change those figures.
Joe