The usual problem on Powerbook and iBook RAM is not inserting the connector edge of the module firmly enough into the socket WHILE it is at the 30 degree angle, BEFORE laying it down to the flat position. It takes moderate pressure from both thumbs to seat it in properly.
You should see none or very little of the module's connectors remaining visible. If you can see more than 1 mm (1/32") of the gold connectors, or if you can see more of the connectors on one side vs. the other, it's not in right.
Thanks
Trevor
CanadaRAM.com