as I know the BM supports not a "real" FTP-Proxy.
In the "BM Bible" is on site 321 written:

The FTP Proxy supports only FTP clients (not browser-based FTP),
though some browsers have some options to be configured to act as FTP
clients. In general, a true FTP client tends to work better through
FTP Proxy than a browser acting as an FTP client, especially if
authentication is involved.

Ok.... so far so good ...

But how you realize a FTP-Connect over a Browser (f.e. IE or Mozilla)?

I installed on a Linux machine the proxy-suite from SuSE but this
don't work together with the IE-Browser on M$ machines.

The workaround over (f.e) GetRight is maybe a solution but is there
(maybe) better solutions?