Using Banshee, I ripped songs from a CD and added them to my library. Then I added the track information to each song, and burned them to a new CD. The problem is that after doing all of that, the new CD still showed "Unknown" for the all of the songs, artist and album. I am using Ubuntu 11.04.
This is the expected result.
When you insert a CD, Banshee tries to get track information from a number of online sources (e.g. MusicBrainz). If it can't identify your CD, you get "Unknown" instead.
Adding the track information within Banshee will not make a difference, because you have not changed the online databases. If the CD is not an officially produced CD, then there's nothing you can do about this. However if it is a published CD, you can add the metadata to MusicBrainz. One way to do this is to install Sound Juicer Audio CD Extractor from the Software Centre and following the instructions.