Here's the info from OWC as they've wrestled with making RAM work on the Apple PB12 machines:
"Author:_OWC Larry
Date:___01-28-04 16:05
When they [Apple 12PBs] were originally shipping, processor sluing was not engaged on the PowerBook 12" Models. But with recent OS updates (and new shipping models), they have been activating that feature. Apple didn't make any change to the memory specifications they publish - but the way this processor sluing technology works, there should have been.
Essentially, with processor sluing engaged, variations in the voltage supplied to the memory bus occur. DDR is supposed to be supplied a standard 3.3v line - but this isn't perfectly the case anymore... and accommodation in the module design had to be done so that the memory can operate correctly with these line voltage variations.
That is the issue.
Larry O'Connor
Other World Computing"
What this means is that generic memory may or may not work with the Apple PB12 machines. This issue is found in both revA AND revB machines.
My advice: buy from a reseller with experience with Macs, and if it acts up at ALL, send it back.