Code:
Failed to fetch http://ppa.launchpad.net/lorenzo-car...source/Sources 404 Not Found
I cannot find that PPA in the Launchpad Index list.


Failed to fetch http://ppa.launchpad.net/songbird-da...source/Sources 404 Not Found
There isn't a PPA for Natty or Maverick.

See Here

Disable them in "Software Sources" and the "404 Not Found" errors should go away.

Good Luck