This message occurs when a script inside Joomla is trying to create a folder but for some reason the permissions on the server will not allow this to happen. Usually the images folder needs to be checked that permissions for it and any files inside are set to something the script can write to. If you use an app such as filezilla as your ftp client you can try using that to set the images folder to 755 and if that fails 777 (in both cases make sure you click the recursive box). If that fails try enabling Joomlas’ built in ftp layer.
