Debian Wheezy : Versions / version names may have a very short life.
2.6.39 was last week. This week it is "3.0.0".
If you want a genuine '2.6.39', then 'squeeze-backports' will supply these:
linux-image-2.6.39-bpo.2-686-pae , linux-headers-2.6.39-bpo.2-686-pae
Today, Wheezy can supply http://packages.debian.org/source/wheezy/linux-2.6
.. from Source Package: linux-2.6 (3.0.0-1) → "linux-2.6_3.0.0.orig.tar.gz"
It is a general thing, that old versions are removed from the server :
To get a matching set of linux-image/linux-headers, then 'linux-image'
must be updated or changed to a supported version.
Debian “wheezy” Release Information http://www.debian.org/releases/testing/