that entry is incorrect in /etc/apt/sources.list.
i may be wrong, but i'm guessing that this entry in sources.list looks something like:
deb ppa.launchpad.net/freyja-dev/unity-tweak-tool-daily/ubuntu/dists precise main sources<br/>
i'm not aware of any repo for sources but you can try taking the sources out of the listing and add this after that line.
deb-src ppa.launchpad.net/freyja-dev/unity-tweak-tool-daily/ubuntu/dists precise main sources<br/>
...again, i wrote that line off the top of my head, but that list at the end of the line appears to be wrong.