TYPOlight is not allowed to create new files on your server. Make sure that the folders system/html, system/logs and system/tmp are writeable and use the Safe Mode Hack to allow file operations via FTP. To enable the Safe Mode Hack, open system/config/localconfig.php and add the following lines:

$GLOBALS['TL_CONFIG']['useFTP'] = true;
$GLOBALS['TL_CONFIG']['ftpHost'] = '';  // FTP host
$GLOBALS['TL_CONFIG']['ftpPath'] = '';  // FTP path (e.g. html/)
$GLOBALS['TL_CONFIG']['ftpUser'] = '';  // FTP username
$GLOBALS['TL_CONFIG']['ftpPass'] = '';  // FTP password

Do not mess with file permissions! TYPOlight will not work correctly if you just make folders writeable. If there are any access restrictions, always use the Safe Mode Hack.