Seu arquivo source.list
está errado. Deve ficar assim:
deb http://http.debian.net/debian wheezy main
deb-src http://http.debian.net/debian wheezy main
deb http://http.debian.net/debian wheezy-updates main
deb-src http://http.debian.net/debian wheezy-updates main
deb http://security.debian.org/ wheezy/updates main
deb-src http://security.debian.org/ wheezy/updates main
Corrija seu arquivo e execute novamente aptitude update
.
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