Hey,
http://apt.puredata.info/autobuild/latest/Pd-0.43.1-extended-ubuntu-lucid-i386.deb seems to be a broken file, as well as the one at
http://apt.puredata.info/autobuild/2012-08-15/Pd-0.43.1-extended-20120815-ubuntu-lucid-i386.deb
The last working i386 deb for Lucid is:
http://apt.puredata.info/autobuild/2012-08-14/Pd-0.43.1-extended-20120814-ubuntu-lucid-i386.deb

András