no problem with a 64bit system
apt-cache policy flashplugin-nonfree
flashplugin-nonfree:
Installiert: 1:3.6.1
Installationskandidat: 1:3.6.1
Versionstabelle:
*** 1:3.6.1 0
500 http://http.debian.net/debian/ unstable/contrib amd64 Packages
100 /var/lib/dpkg/status