I'm having the same problem. I am administering a site for a friend, and the account has been active for years. Roughly two years ago I uploaded the current version of his site, and throughout the last two years, I've had to FTP a file or two, and never had a problem.
I'm working on a new version of his site, and went to upload some of the files today, and the FTP account I've always used is not working. I attempted changing the password, but I still keep getting a 530.
I also tried creating a new FTP account, same problem. any ideas?
Nevermind. For some unknown reason, it's working. I tried logging in with Filezilla, which has the old credentials stored, and it worked with the old unchanged password.
Completely confused, but I don't really care, as long as it's working.