I've recently upgraded to an Optic Fiber internet connection and my Xbox doesn't seem to be able to wirelessly connect to my modem ever since. Bear in mind, I was able to connect to Xbox Live while I was on my old modem.
Apart from not being able to connect successfully, each attempt of connecting the Xbox actually interferes with my modem as well and I will not be able to surf the internet from my computer. I have to reboot the modem to solve the error.
Would like to hear from the experts.