The other Internal Service Error threads I've read have not given any my any info to solve my problem. I have deactivated all plugins and it's still a problem. When I activate NextGen but not Pro, I get the following message where my gallery should be:
Default Gallery Type Template
This is the default gallery type template, located in:
/home/pnventer/public_html/wp-content/plugins/nextgen-gallery/products/photocrati_nextgen/modules/nextgen_gallery_display/templates/index.php.
If you're seeing this, it's because the gallery type you selected has not provided a template of it's own.
Example: http://pnventerprises.com/clients/alger
I can't find any way to change the template for any of my galleries. My host says there is nothing changed otherwise. When I re-activate Pro, the Internal Server Error comes back. It is currently deactivated, but regular NextGen is active.