They changed the rules again. From the ES instructions:
Installment Payments – Installments due for each taxable year beginning on or
after January 1, 2010 shall be thirty percent of the required annual payment for the
1st required installment, forty percent of the required annual payment for the 2nd
required installment, no installment is due for the 3rd required installment, and
thirty percent of the required annual payment for the 4th required installment.
Installment Payments – Installments due for each taxable year beginning on or
after January 1, 2010 shall be thirty percent of the required annual payment for the
1st required installment, forty percent of the required annual payment for the 2nd
required installment, no installment is due for the 3rd required installment, and
thirty percent of the required annual payment for the 4th required installment.