jpegs broken from upload

Hi,
Every time I upload a jpeg into a gallery in nextgen the images break and only as a blue box with a [ ? ] inside. This occurs whether you upload into a new gallery or into an existing gallery that has worked fine for years. I also get this error if you upload the photos direct to the server and then “scan for photos” when you log in through wordpress. I also get this error when uploading photos that have previously been uploaded and work fine (so its not a file type issue).
I had hoped that this might of been fixed with the past few updates to the plugin but alas…. looking forward to your response!
Cheers, Ell

http://wordpress.org/plugins/nextgen-gallery/