[Export does not work]

It does take a long time, but at the end it worked.  Thank you.   

[Export does not work]

I am exporting my project into PDF.  I am using iMac mid 2011 with 12 GB and OS 10.7.5.  When I am exporting a processing bar appears  and stays on for a very long time ( a few minutes).  The activity bars shows high CPU utilization.  I end up forcequiting.    I did try that by exporting into PNG and it was the same experience.  What am I doing wrong?

 

Thanks