slider image doesn't change

Hello!
I have only 1 image in the slider.
When I remove the image and i use the url of a new image, the frontend doesn’t refresh it, but when I uncheck “Check this to Enable Slider” the slider dissapear, but when I mark the check to show the slider again it show the old image.

In the backend the image keeps changed but not in the frontend…

Anybody knows where can be the trouble?

Thanks a lot!