Order Manager Export

I have tried to export the Order Manager so I can view the headings in each column, then add the listings from the non-responsive theme into the .csv (of the responsive theme) and reload it all back into the (Responsive) theme.

I have only loaded one order via Admin. When I click “export all orders” I get a white screen.

I have typed into .htaccess the following:
max_execution_time = 18000 ;
max_input_time= 18000 ;
memory_limit = 512M ;
upload_max_filesize = 20M ;
post_max_size = 20M ;
php_value memory_limit 64M

Any ideas of what is causing the white screen? Is it because I only have the one order?