Error preventing FTP upload: "Invalid command specified"

[perkincr]

I'm using the FTP component in Visual Build. Sometimes I get the error message "Invalid command specified ('ORT 67,135,146,250,19,139": command not understood).

Knowns:
I don't get the error on Win2000. Running WinXP I do.
Enabling passive mode seems to eliminate the error.
One website seems more prone to error than another.

It seems that the command is not being fully communicated. 'ORT' included in the error message may be a portion of the 'PORT' command.

Does anyone have insight as to what causes this error? Why would the command request be truncated?