This problem has been occurring for the past 2 weeks every time I use Firefox on each of the 2 PCs I use everyday. The problem may occur a few minutes after starting Firefox or it may be hours of continuous use before the connection is lost. It doesn't matter if I'm running Firefox by itself or have background apps running, but definitely requires Firefox to be running before I see a problem. Configuration: WIN 8.1 and VISTA 64; both with latest updates. LAN: cable modem and Belkin wireless router; both with latest firmware. Firefox v37.0.1 with no add-ins or add-ons. Start page is "blank". Symptoms: Windows status bar shows I am disconnected from the router. Router and modem status LEDs show I am connected to the internet. Same for the WIN network status app. It shows no router connection. The problem can be temporarily fixed by power cycling the router. Or, by just waiting a random period of time the connection may (or may not) be reestablished on its own. I also use a standalone PC application that streams text data in short bursts and runs all day (no video or music... just short lines of text) with no problems until I start Firefox in the background. Then it may go a few hours before the connection to the router is lost. I also frequently watch videos on my tablet with no problems from the router. While typing in this question on a PC I was disconnected from my router. I'm hoping to get some suggestions as to what to inspect or change. Thanks!