Everytime I go to export my progect in Cubase 5 it neglects to export the audio tracks I have recorded and only exports the virtual instruments. Someone please help! This just started out of nowhere… 
I have seen tracks left out before. It was only on my old machine though. What are your system specs (processor and memory). Have you tried a real time export and/or freezing some tracks before exporting? That always seemed to do the trick in my case. I have since acquired a new computer on which I have never had the problem again.
HTH
J.L.