From: Sunnyvale, CA (Unite
When you launch NeroMix, go to Preferences and under General->Recorder Control, make sure you have the Input/Output selector enabled, and not the Wizard.
Now when you go back too the main window you should have two buttons. One to select the source, such as File or Line-IN, and one to select the output format such as WAV, AIF, or MP3/MP3Pro.
Are you now able to see the MP3 option?
I did test with the latest release on our website and all appears to be working.