[Plugin: NextGEN Gallery] Uploading images works, but doesn’t upload thumbs (“Thumbs” folder empty)

I have a very, what would appear to be, basic problem.

I’m trying to upload images (in my gallery), and the images themselves works just fine, but the thumbs doesn’t. NextGEN have created the “thumbs” folder as it should, but the folder itself is empty.

I am given no error messages at any time when uploading, the thumbs folder is just empty.

I have made sure the “gallery” and “thumbs” both have 777 permission. I have also made sure GD lib (greater than) 2.0 is installed and working (it is also able to watermark images).

Please advise.
Thanks.