Customers have reported this behavior with some, but not all, modems that receive power from the Apple Desktop Bus. Modems with a dedicated power supply that plugs into a wall outlet do not show this issue. If restarting or shutting down and starting up the computer does not seem to make a difference, then either resetting your modem (assuming it has a reset button) or disconnecting and reconnecting the modem's ADB cable should resolve the issue.