Package netpbm not found during debian wheezy 7.6.0 net install

[Alphonse Ogulla <aogulla@gmail.com>]

debian-7.6.0-amd64-netinst fails at "Select and install software" when
retrieving file 1204 of 1315 (26%).

Further investigation on the 3rd expert install attempt shows that the
installer cannot progress past downloading package netpbm amd64
2:10.0-15+b1

messages in Ctrl+Alt+F4 console window are as follows:

Aug 11 16:18:08 in-target: Get:1452 http://debian.mirror.ac.ke/debian/
wheezy/main netpbm amd64 2:10.0-15+b1 [1,349 kB]
Aug 11 16:18:15 in-target: Get:1453 http://debian.mirror.ac.ke/debian/
wheezy/main netpbm amd64 2:10.0-15+b1 [1,349 kB]
Aug 11 16:18:22 in-target: Get:1454 http://debian.mirror.ac.ke/debian/
wheezy/main netpbm amd64 2:10.0-15+b1 [1,349 kB]

I get the same results with different mirrors i.e.
http://ftp.nl.debian.org/debian/ and
http://debian.mirror.ac.ke/debian

I'm trying to install debian wheezy 7.6.0 using the net install image
debian-7.6.0-amd64-netinst.iso which I downloaded using Google Chrome
and burned onto a USB flash drive using dd package for Windows 7.

Rgds,
Alphonse Ogulla
Nairobi, Kenya