ram upgrade problem

hi all.

i have a 2ghz macbook pro installed with one 512 and one 1gb memory module.

i bought the laptop from a mac refurbisher who assured me that if i needed more ram i could buy a 2gb stick and add it to the 1gb already there to make 3gb total. i have read that the 2ghz mbp's don't read more than 2gb memory, but thought i'd give it a shot anyway, and that the machine would at least read 2gb of the total 3gb installed.

anyway, i bought a 2gb stick from pny, recommended fro mac use. popped it in no problem, but on hitting the power button, got no chime, and no image on screen, just the standby light on the lid lock button came on.

tried all combinations of 1+2 top and bottom, and also tried the 512 with the 2gb. but all produced the same result. i'm pretty relieved that the machine works again with the original configuration reinstalled.

so, should i sell the 2gb stick, move on and install 2x1gb, or is there some other reason why this process didn't work?

thanks for your advice in advance.

john.