audio mixdown

I use the AI 4, 4.5.2

When I try to export a project to an MP3 file I get the message “Unexpected error”.

Why is that ? What can I do?

The export/audio mixdown function with other songs …


Export as wav and use iTunes or Lame to convert to mp3.

But it function with other melodies …!
it is only one song, so fare, that get this message …

What does the project contain for plugs?