I have a powerbook g4 running leapard 10.5.6 I recently upgraded the ram from 1 1g module to 2 2g modules. It will not start with both modules in at once (2g,2g) but it will start with one of the two in and the second port empty (which port is empty doesn't matter). When it has both in it beeps once and doesn't start. Any idea why this would happen and/or how to fix it? thanks.