550 Requested action not taken

Hello,

I searched the forum and google but couldn't found any solution.

When I try to create dir, remove dir, upload file or any other changes, I get the following error:

550 Requested action not taken

No other information available however.

The strange thing is that when I try to do the same thing with the Windows/FreeBSD ftp clients there's no problem.
When I connect to other host using SmartFTP I can make the changes.

Any ideas/suggestions?

Thanks in advance!