I have also problem with export subscr.
When I try to export via chrome and opera. I see the message Error:network error.
PHP settings:
max_execution_time 600
max_file_uploads 20
max_input_nesting_level 64
max_input_time 60
max_input_vars 3000
memory_limit 256M
output_buffering 4096
post_max_size 40M
Permission on WordPress folder (and subfolder) – 750
and files – 640
Small list of subscr. (5 e-mails) well done.
And 500 subscr. – cause error.
Thanks, Pavel.