[Seven Skins]

Attachment.php line 388 to 397.

PHP Code:

if (in_array($extension, array('jpg', 'jpe', 'jpeg', 'gif', 'png')))
{
    header("Content-disposition: inline; $filename");
    header('Content-transfer-encoding: binary');
}
else
{
    // force files to be downloaded because of a possible XSS issue in IE
    header("Content-disposition: attachment; $filename");
} 


If you remove the ELSE statement may be it will work. (While you figure out what is causing an issue.)