Good morning Ashley,
Thanks for the reply and tip.
The above mentioned file was 00:00:00 in lenght, I added some padding to make it 00:00:01 in lenght and it imported successfully.
I will keep that in mind and post back here later when I have completed a few more imports.
So it's true - you learn something new every day!
FYI: Free Audio Converter converts all the files to OGG and AAC without any problems.
Thanks for your help.