Failed to fetch http://ppa.launchpad.net/tualatrix/p...source/Sources 404 Not Found
Failed to fetch http://ppa.launchpad.net/tualatrix/p...-i386/Packages 404 Not Found
Some index files failed to download. They have been ignored, or old ones used instead.

Also, there's a red triangle with an exclamation mark too. How do I fix it?

At first, these are not Ubuntu's repositories, these are third party repositories.

To fix them just replace the /pp/ with /ppa/ in the address.

How do I replace them? What command? Now that you mention it, I did add a repository or two for Ubuntu Tweak.

Open the Synaptic package manager and go to Configure sources or something like that (currently no Debian based install here, I can't say precisely). Then seek the two entries and edit them.
I don't know for sure, but you may also be able to correct them in the /etc/apt/sources.list or in one of the files in /etc/apt/sources.list.d/ .

system-admin-software sources-other software

Akuthia got it.
And here is a tutorial on adding and removing third party repositories: https://help.ubuntu.com/community/Repositories/Ubuntu
And specifically for PPAs: https://help.ubuntu.com/community/Re...#Adding%20PPAs
And for removing PPAs: https://help.ubuntu.com/community/Re...20Repositories
You can also install ppa-purge to completely purge packages installed from PPAs: http://www.youtube.com/watch?v=my0kqbro6og
You can search for PPAs here: https://launchpad.net/ubuntu/+ppas
You should use those PPA repos sparingly though. They vary widely in quality, and can induce dependency issues and other problems.
I believe that many, if not most, of the Ubuntu dist-upgrade failures are caused by the boatload of third party packages that so many people add to their Ubuntu systems.