Just on the "Passive" aspect again (which may be a red herring) - what happens if you set Passive => 1 in the new() constructor ?

Here's what perldoc Net::FTP has to say about that:

Passive - If set to a non-zero value then all data transfers will be
done using passive mode. This is not usually required except for
some *dumb* servers, and some firewall configurations. This can also
be set by the environment variable "FTP_PASSIVE".
[download]

Update: You might want to try that (both with and) without the $ftp->pasv();

Cheers,
Rob