ok, i have only tried booting and "original" ps2 disc twice and it worked fine..
im assuming u r using NEO2, right?
if so, turn on ur ps2, put in the PSX original and then put it in sleep mode - ie so it is on at the back but the green light is red.
then, turn it on and hold the power button until the blue tray light comes on - approx. 1 second.
to play PSX backups they should just boot automatically - if not u dont have a NEO2 chip? or have installed wrong??
hope that helps!