When ever i hover the thumbnails the image disappears and turns white.

vesterhavsrock.mp-marketing.dk/index.php?view=article&catid=3%3Agalleri&id=2%3Abamsesvenner07&option=com_content&Itemid=4

Please help me fix this issue.

Thanks in advance

which engine are you using?

There is a little file called stripes.gif in

/public_html/plugins/content/jwsigpro

which is what I see when I hover on your images BUT it is really big compared to the thumbnail size. (a big rectangle)

I would check the setting of size for the thumbnail in the plugin set up.

And try out another engine to find out that is compatible with your set up.

I am looking at the site in Firefox 2.0.0.14, it will probably behave differently in IE and other browsers.