Hi,
I found the culprit: it seems to be an CSS error of the WordPress backend.
A modal window is opened, that can’t be scrolled or used in any way because the greyed out area is above the modal window content, it’s a z-index error that’s caused by #TB_overlay / thickbox.css.
If you add the following to the functions.php, the error is removed.
add_action('admin_head', 'modalwindow');
function modalwindow() {
echo '<style>
#TB_overlay {
z-index: 1;
}
</style>';
}
It’s strange that this error only occurs when I use your theme, but it may just be a strange coincidence.
Thanks for looking into it.
Best regards!