i think the problem is caused by THICKBOX, but i still don’t know what to do about it.
when i use SHUTTER, it works fine.
Although Shutter blows-up the images that big, that the navigation is falling of the page.
And the navigation of Thickbox is more suitable that Shutter, but oke.
So if anyone has een solution for the Shutter-size problem, then i’m happy as well.