Comment 1 for bug 164135

This is unlikely to be a bug, and more likely to be exactly what the error says. You probably have an incorrect entry in /etc/apt/sources.list.

Use ALT+F2, gksu gedit /etc/apt/sources.list
Then locate line 77 and correct the format of the line. Each line should normally start with a # if it's a comment or deb or deb-src.