You have a Panel login here, and then there's an FTP user login. How did you get your logo onto your site?
That message usually means that your username or password is incorrect. It won't tell you which one, but it could be both, in your case.
Your FTP user is listed in the panel for Manage Domains. If you're sure you have the right user, you can change the password under Manage Users. Remember that only that user has FTP access to your site. Your panel login or other FTP users you created can't FTP to your site directory.