I am trying to access my web site throught the command prompt using FTP.

I frequently get error messages like the following:

500 "PORT 151,213,155,136,114,91 ": command not understood.
Connection closed by remote host.

This error message appears at random times after random commands. The port
number varries. I think the most frequent command this happens after is
"dir".

Does anybody have any ideas how to fix it?

Matthew