Question:   I just changed my FTP username in plesk and now suddenly my FTP user doesn't have permissions to my domain's directory structure (can't ftp upload or download files, or even browse the directory structure).

Answer: This is a known issue with Plesk 8.6, and we have contacted Parallels for a fix. Basically when you change the ftp username, plesk removes the permissions for ftpuserA, and applies permissions for ftpuserB... the bug is that it doesn't complete the second step properly.

We do have a workaround for this, and can properly apply permissions as necessary if you change your FTP user and are affected by this.  Simply submit a request to the Support team, and they can correct the issue for you.