My wife's HP ENVY m6-1125dx PC using Windows 8 with Ralink RT5390R 802.11 bgn wifi adapter would lose wifi connection with the VERIZON FIOS Actiontec MI424WR router after 13-14 minutes; plugging the ethernet cable in would regain internet access, or restarting the PC but the issue would return in 13-14 minutes. My Toshiba laptop, using Windows 7, stayed connected when my wife's laptop lost its wifi connection. The other devices in our house (Wii, TIVO, printer, etc.) had no connection issues. Interestingly, my wife's laptop did not lose its wifi connection at other hotspots (Best Buy aka Geek Squad, McDonalds, Starbucks, Panera, etc); so the issue was specifically between the Ralink wifi adapter and the Actiontec router wifi.
Just updating the laptop wifi adapter driver did not fix the issue. HOWEVER, uninstalling the wifi adapter driver then reinstalling the latest driver from the HP website seems to have fixed the issue. Also installed the Intel Wireless Drivers for Microsoft Window 8 from the HP website.