At this point you will have to rely on dpkg if you think it's worth the time.

Open a shell and type:

Code:
man dpkg
You will likely have to force the removal of apt and then install aptitude or reinstall apt from .debs that you manually download, for example
Code:
dpkg -P --force-depends apt
Which leaves you without apt-get. Got to http://packages.debian.org/sid/i386/apt/download

then try
Code:
dpkg -i apt_0.7.10_i386.deb
as root, from the directory that you downloaded the .deb to

You should then be able to download aptitude from http://packages.debian.org/sid/i386/aptitude/download

and use dpkg to install it.

Good Luck