Gallery STUCK

Hi,
I was uploading images to a gallery I’ve been using many times before. Always the same way and same type of files (size and resolution). As it was generating the thumbnails it got stuck and browser won’t keep loading. If I go into manage gallery thumnails of new images are “broken” and it isn’t even possible to delete them. I tried to create a new gallery and upload them there but problem persists.

Solution?? Thanks a lot
David