I may have read something about this previously but I can't find it

We have a small branch office set up as a slave S2S VPN to our master. Allw
as well a few weeks ago until they moved the office.

They were on a DSL line and BM3.8 worked fine. Since they moved the only
high-speed ISP available was the local cable company - Comcast. The S2S and
most proxy services work fine however they cannot access secure FTP sites.

Nothing has changed except the ISP. Is this an unsolveable issue and did I
indeed read somewhere that some cable companies use their own proxy servers
that may confuse BM? Thanks.