uploading seems to be limited to about 3260 pages, the third upload locked site

I have 3000 or so pages active and 6000 in drafts the fourth upload broke the pages admin access when you try and go to the pages folder this error comes up. there is no server problem.

The website encountered an error while retrieving https://www.silverstarsat.com/wp-admin/edit.php?post_type=page. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

what are the limits how did i break it and what is the fix

http://wordpress.org/extend/plugins/bulk-city-landing-page-creator/