Cannot insert images into posts

I am using a bootstrap template that I wrote from scratch — several months ago I created a blank template that I use to build websites. I copied it to this WP install and started customizing it. I’ve been using this exact same theme on various websites and have not had any problems.

There appears to be some sort of conflict between my theme and the media manager. These are the symptoms:

1. I am able to upload files through ‘Media’ without any problems.

2. When I am in a post and I try to ‘Insert Media’, my image gallery does not load — it just clocks indefinitely. If I go to insert an image, it looks like it has uploaded, and then at the end there is a generic ‘File Upload Error’. message.

3. I then go to ‘Media’ directly through the dashboard and the image is uploaded and appears in the library.

4. I only have this problem with actual image files — I can upload and insert PDFs with out any problems.

5. I am only running a few plugins but tried disabling them and still have this problem.

6. I switched to other WordPress Themes (like 2012) and my problem goes away — the image insertion works fine.

7. I went to another website that is running WordPress successfully and uploaded my theme. I had the exact same file upload problems, so that just reconfirms that the problem is specifically with this theme.

8. I am not getting any javascript errors and there is no PHP error. I checked with my hosting company and there are no issues in the server log and everything appears to be set up correctly.

Your assistance in resolving and troubleshooting this problem is much appreciated!