RAM reset after resetting PMU

[gregplancich]

Right, I posted here yesterday about my 12" PB not booting up. Somehow I managed to fix that. However, since I reset my PMU, some of my RAM has disappeared. Before I reset it, in the "About this Mac" it said I had 512 MB of RAM. Now, it says I only have 256MB. How can I fix this?

 

[CanadaRAM]

Suspect either a bad RAM module (may have been the cause of the original problem) or you accidentally unseated it. Try removing and reinstalling the RAM module, making sure to seat it all the way into the socket.