Orbit Downloader recently brought our LAN to a halt.  Where we should have been getting 2.2 mbps, we were getting 0.15 mbps.  I eventually performed an isolation test along with some bandwidth tests.  As soon as the offending PC was plugged into the LAN, the internet speed immediately dropped for all LAN users.  Very nasty.

To turn it off, open Orb preferences and untick this box:

Alternatively, just uninstall Orbit altogether.