I've got a situation where we are using Events+ with front-end posting of events so users can add events.
The site is on a secure server behind a firewall, but I also have a duplicate on the internet here for troubleshooting. http://dev.prometheusfire.me/act-connect/
On the add event page http://dev.prometheusfire.me/act-connect/events-calendar/add-or-edit-event/
On this dev site the featured image upload works for subscribers, but stalls at crunching. Okay fine, I found that the Add Media button in TinyMCE works okay, but subscribers get the error "You don't have permission to attach files to this post."
It works fine for admins and I have a User Role Editor plugin installed and have given the right permissions to subscribers, but am having no luck in beating the error.
I've activated support access on the dev site. If you are able to discover a solution, please inform me of everything you did as I have manually carry them over to the live site on the internal server.