Well the title of this thread should say it all.
Anyways, I created a folder in all capital letters, and wanted to give somebody access to upload some files.
However through SiteWorx|FTP Accounts, giving just access to my newly created folder created an error “Directory invalid”
So after having checked folder permissions, and checked access to another folder worked, a folder in all lowercase, I renamed my newly created folder to all lowercase, and then I could create FTP access for that folder.
Clearly a bug…