Hi wizart85,
I understand that this error can come out for many reasons.
In my case I solved by removing the exif data from the image. You can use ewww plugin to remove exif data on image uploading and then load images from media gallery to nextgen gallery.
I’m getting the same error:
“Could not write to file. Please check filesystem permissions.”
I tried on different servers with a clean wordpress installation end I get always the same result.
I’m able to upload images only if I remove the exif data from the jpg.
Is something missing in the server configuration?