1st Generation Apple TV not connecting to wireless (Apple Express) when turning on secuirty?

My Apple TV first generation worked fine until I switched from a Verizon Wireless router to the new Apple Express. The Apple TV does connect if I turn off secuirty. It also connects if I do a factory reset but then loses connection when I upgrade to the latest Apple TV First Generation S/W. All other device (MAc Book Pro, IPAD, and 2 iPhones, Roku and PS3 work fine. Tried different channels to no avail. Any help would be greatly appreciated.