Image attachment: Lightbox works, thumbnail turns black
 

Hi!

When i attach a JPG-image to a post i get to see this:
http://www.deorvanheemskerk.nl/bugs/lb1.JPG
But the LightBox itself works when i click on one of the thumbnails:
http://www.deorvanheemskerk.nl/bugs/lb2.JPG
But i don't know what the problem is with this thumbnails... :(
How can i fix this?
Greetz,

tijmen_4real