Powerbook memory upgrade

They can be different capacities.

 

Getting Started Guide has required info

Check out the section SUPPORT>MANUALS and do a search using "replacing RAM expansion card Powerbook G4".

This brings up a list of manuals for each specific Powerbook.
Open the relevant "Getting Started" Manual and go to "Adding Memory to your Computer" - this tells you what you need to know regarding capacity, access to the RAM cards, slots etc.

I am in the process of doing the same thing but seem to have encountered a problem:
I have a 15" Powerbook 1.25GHZ (basicllay the same config as the 1.33 - 1.5GHz model, with Superdrive. I tried to install a 1GB card in the top slot, leaving one of the original 256 cards in the bottom slot.
When I restarted, it made all the sounds as though it was starting up, but my screen remained black. I tried a restart several times.

I then changed the new card back for the old 256, and restarted, only to find that not all my keys work now, so I am unable to log in using my password.

Not sure why any of this has happened - I bought compatible RAM according to the manual, so just be aware that it isnt as easy as it seems...

Anyone have a solution for me?
Lisa