You haven't explained your setup, but I assume you have a DSL modem, then a router, into which the OBi is plugged in?
If so, one thing to check is the IP address of each device. The DSL modem is likely a static IP, often printed on the bottom of the modem. That IP address COULD be conflicting with the OBi, depending on how you set things up. This is a long shot, you probably have the DSL modem connecting to the router and the OBi connected to the router, so the DSL modem is getting an address from the router which should not conflict with the DSL modem, but it's worth checking.
My former AT&T DSL modem (forget the brand) had a static IP that conflicted with another device, so I had to go into the modem setup and change the IP before hooking into my network to get around the problem.