Switched on machine and i heard the tone. Then i heard the just fading out end of the tone again and the screen stayed white, no boot. Pushed power button, same thing. Unplugged at the back, powered on and that sorted it. However I remain nervous. Has anyone else ever had this problem or know what might have happened? 
Mac Pro 2008 2 x 2.8ghz quad core. 10.6.8 8gb ram (8x1gb sticks)
Mac Pro 2008 2 x 2.8ghz quad core. 10.6.8 8gb ram (8x1gb sticks)