FTP - I can connect OK, but whenever I try to upload files it fails!

Please make sure you are uploading your files into the httpdocs directory as this is where all your web content resides. If you using Plesk 10 and have multiple domains set up on different directories, then be sure to upload your files into the directory you created for the associated domain.

If you are still unable to upload the httpdocs directory, you will need to enable Passive mode. See here for instructions on enabling passive mode.