Image container empty after relaunch

Hi,
after we moved from our sandbox onto our server all “post-images” are gone.
usually you find the output of the image in a <div> :
<div class=”image-container”></div>

But this container is empty now.
We tried to run the plugin “regenate Thumbnails” but that didnt help.
An error ocuured :””china-akrobatik” (ID 1811) failed to resize. The error message was: The originally uploaded image file cannot be found at “

what to do now?

Example:
http://www.musicandartists.de/kuenstlervermittlung/akrobatik/