Recently I refurbished a Macbook A1181 (version 4.1 , the one @2.4Ghz) and I had the same issue.
When I finished the repair and mounted the keyboard and trackpad back on, as well as the battery, I realized they where not responsive, despite the power button still worked.
I read in a forum there was an issue with this particular model and the ground level, making that both the keyboard and the trackpad don't work.
What I did was sticking a tiny little piece of a plastic sheet between the metal case and a little gold V-shaped connector that is spotted in the left side of the battery connector board (if you watch it from the pins side), to avoid contact between them. This worked for me.
Hope this helps.