Dual monitors with laptop docking station

Hello,
Have a Hp laptop that is docked, I have two monitors connected a 24inch Hp LP2465 wide screen and a Hp L1908w 17 inch. The connection for the 24" is with normal serial cable and the 17 is with the new style cable with the muli prongs. Only the 24 inch is on. the computers reconizes the the monitors but the 17 says no input signal. Whats wrong?