Adobe Flash Player verion 10 on Debian Lenny for 64-bit (amd64)

Debian wiki flash player info

download this:
http://packages.debian.org/sid/amd64/flashplugin-nonfree/download

Then, as root, run this to install the .deb package:
dpkg -i flashplugin-nonfree_2.8.2_amd64.deb

Restart your browser (e.g. firefox or icedove)