Moitor and sart up problem with acer t180

please can anyone help me i have recently upgraded my monitor from a xerox 19'' to a samsung 23'' syncmaster now with the monitor in standby i turn on my acer t180 and the green light in the on button dosent light up an the monitor wont detect a signal if i turn off both pc and monitor then turn the pc and then the monitor everything works fine in this pc i am running a xfx 9500 gt graphics card and have the latest drivers for the card and monitor so why should this be. i know its only a little problem but it is buggin me rotton so i would be grateful for any help thanks