Been having the same issue but with this fatal error message
Fatal error: Out of memory (allocated 35651584) (tried to allocate 6176 bytes) in …/wp-content/plugins/nextgen-gallery/products/photocrati_nextgen/modules/nextgen_data/package.module.nextgen_data.php on line 3977
I have this same problem and in addition when I created a new gallery with the same name and containing the same images after the delete I get upload errors. When I looked in the gallery folder on the back end I see that ALL of the deleted gallery folders are still there along with all the images. Nothing is actually deleted at all. I deleted the folders from the back end but the front end seems unaware of it and I still can’t create a gallery with the same names as one I deleted and upload the same photos.
