HELP!!!!!

For no reason at all, my Cubase 6 has stopped exporting audio!! I just get blank files of silence now.

I didn’t change any settings, uncheck any boxes… nothing. Just silence whenever I export an audio file, whether mp3, WAV, whatever.

I tested a short 30 second export and it had sound - a bit longer and nothing.

What happened?!?! Anyone have any clues??!!