PHP connector Upload problem with Javascrip integration

I am testing FCKeditor for a new Web site and I am having problems making the upload work (Seems a lot of people do too...
The file browser is working fine, so my path is OK, but when I try to upload a file, I get an "Invalid file type" message. The file is a png image and my connector config is as follows:

$Config['AllowedExtensions']['File']   = array('gif', 'jpeg', 'jpg', 'pdf', 'png', 'rar', 'txt', 'zip') ;
$Config['DeniedExtensions']['File']      = array('7z', 'aiff', 'asf', 'avi', 'bmp', 'csv', 'doc', 'fla', 'flv', 'gz', 'gzip', 'mid', 'mov', 'mp3', 'mp4', 'mpc', 'mpeg', 'mpg', 'ods', 'odt', 'ppt', 'pxd', 'qt', 'ram', 'rm', 'rmi', 'rmvb', 'rtf', 'sdc', 'sitd', 'swf', 'sxc', 'sxw', 'tar', 'tgz', 'tif', 'tiff', 'vsd', 'wav', 'wma', 'wmv', 'xls', 'xml') ;
$Config['FileTypesPath']['File']      = $Config['UserFilesPath'] .'Files/' ;
$Config['FileTypesAbsolutePath']['File']= ($Config['UserFilesAbsolutePath'] == '') ? '' : $Config['UserFilesAbsolutePath'].'Files/' ;
$Config['QuickUploadPath']['File']      = '' ;
$Config['QuickUploadAbsolutePath']['File']= $Config['UserFilesAbsolutePath'] ;

$Config['AllowedExtensions']['Image']   = array('gif','jpeg','jpg','png') ;
$Config['DeniedExtensions']['Image']   = array('bmp') ;
$Config['FileTypesPath']['Image']      = $Config['UserFilesPath'] . 'Images/' ;
$Config['FileTypesAbsolutePath']['Image']= ($Config['UserFilesAbsolutePath'] == '') ? '' : $Config['UserFilesAbsolutePath'].'Images/' ;
$Config['QuickUploadPath']['Image']      = $Config['UserFilesPath'] ;
$Config['QuickUploadAbsolutePath']['Image']= $Config['UserFilesAbsolutePath'] ;

$Config['AllowedExtensions']['Flash']   = array() ;
$Config['DeniedExtensions']['Flash']   = array('swf','flv') ;
$Config['FileTypesPath']['Flash']      = $Config['UserFilesPath'] . 'Flash/' ;
$Config['FileTypesAbsolutePath']['Flash']= ($Config['UserFilesAbsolutePath'] == '') ? '' : $Config['UserFilesAbsolutePath'].'flash/' ;
$Config['QuickUploadPath']['Flash']      = $Config['UserFilesPath'] ;
$Config['QuickUploadAbsolutePath']['Flash']= $Config['UserFilesAbsolutePath'] ;

$Config['AllowedExtensions']['Media']   = array('gif', 'jpeg', 'jpg', 'png') ;
$Config['DeniedExtensions']['Media']   = array('aiff', 'asf', 'avi', 'bmp', 'fla', 'flv', 'mid', 'mov', 'mp3', 'mp4', 'mpc', 'mpeg', 'mpg', 'qt', 'ram', 'rm', 'rmi', 'rmvb', 'swf', 'tif', 'tiff', 'wav', 'wma', 'wmv') ;
$Config['FileTypesPath']['Media']      = $Config['UserFilesPath'] . 'Media/' ;
$Config['FileTypesAbsolutePath']['Media']= ($Config['UserFilesAbsolutePath'] == '') ? '' : $Config['UserFilesAbsolutePath'].'Media/' ;
$Config['QuickUploadPath']['Media']      = $Config['UserFilesPath'] ;
$Config['QuickUploadAbsolutePath']['Media']= $Config['UserFilesAbsolutePath'] ;