Can you run the Xbox live connection test and post up the error codes it comes up with when you press Y?
So concentrating on just using wired for now, can you reset your Xbox network settings to factory defaults (and then leave the Xbox settings alone) and try to connect wired again to the router.
If that still fails on ip address failed can you connect the Xbox directly to the Cable modem. Power off the modem, power off the Xbox. Power up the modem and wait 2mins, then power up the Xbox and try to connect.
Let us know the results and when you want to connect your router back up to the modem just power the modem off first