The allvideo player creates a column with the samen width als the player, wich causes a large page downwards.

See: lahurqueinternational.com/page/index.php/brands/itchie

How can I solve this?

Your template's css has a generic statement for the images (img {height:auto !important;}) which causes your issue.
Either remove the !important from the height of the above statement located in templates/theme1139/css/skeleton12.css or add this to the end of your template's CSS file.

.avPlayerWrapper .avPlayerContainer .avPlayerBlock div img {height:100% !important;}

Thank you so much Yiota! Problem solved  :D

I had no clou were to look for the fix... Big thnx again