Hello,
Perhaps a closer inspection of the HTML might change between the state
of open or closed. This could be handled by the class of the DIV tag
or CSS style.
When the Colorbox is open the div tag may have a class='colorbox
selected' or a specific style. When the colorbox is closed the div
tag my have a class='colorbox'.
Use firebug to inspect the element and see if there is a key
difference between these two states.
If you still have trouble please post the HTML.
Good luck,
Carl