I've just been reading through a thread on this issue, however the comments are now closed so I thought I should open a new one.
My problem is very similar to those described by other users. When I upload an image to a selected gallery, I recieve a message telling me that upload was successful, and I have successfully uploaded 1 image. However, when I then visit 'manage gallery' the image i've just uploaded is not there. I've tried 'searching for new images' and nothing is found. I tried uploading the same image 3 times, recieved '1 image successfully uploaded' each time but again nothing has been added to the gallery.
If anyone could advise me how to fix this problem, and why it is happening. That'd be hugely apprechiated. The NextGen gallery is the most important aspect of my website since I'm an artist & the website is my online portfolio.