Perhaps Nero killed it, but i doubt that. You should be able to get your correct functionality in a product once you reinstall it.
But that doesn’t solve the issue at this moment. I have no clue why Roxio doesn’t do mp3 anymore or why Nero might have killed it, but may i suggest a 3rd product for making your own mp3s by ripping audio cd’s? Get ExactAudioCopy. Stable as hell and rips about every audio cd with ease. Along with the Lame mp3 encoder it can easily make mp3s out of your ripped cd’s.