RAM not detecting

hi all

Thank you in advance for those who will help

well I have been a mac user for 3 years now, and have never had any problem
with my imac G4 1gig 17 inch flat panel.

I have been running on low RAM for a while now (512mb) especially that I do alot of graphic work. Since my switch to 10.4. I really needed to upgrade.

So I added a 512mb DDR 226 on my newly freed slot and my computer does not detect it. Tried a few times to reinstall, even made sure that I had RAM that was compatible, and still I have no idea why it doesnt detect.

Does anyone have any suggestions? Should i return and buy a different brand of generic RAM?

any advice would be appreciated