Well, it doesn't get corrupted when I try it from here:
% wget
http://ftp.us.debian.org/debian/pool/main/g/glibc/libc6_2.2.5-6_i386.deb
...
% md5sum libc6_2.2.5-6_i386.deb
d15fc9c0e770728f580f934d36aeaf9f libc6_2.2.5-6_i386.deb
% wget
http://ftp.us.debian.org/debian/dists/woody/main/binary-i386/Packages
...
% grep-dctrl -F Package -X libc6 -s Md5sum -n < Packages
d15fc9c0e770728f580f934d36aeaf9f
That seems to be the same checksum.
What is the exact error message from the install program that complains
about it?