I'm not saying that it is the problem, but it is definitely something to consider.
Something you might think about, is if you have another computer in the house that is hooked directly to the internet, rather than using the hub, you might consider getting a 5GHz only router and setting up a totally separate 5GHz LAN for only the 360.
As it is, I going to go to a separate ( and more secure ) non-internet 5GHz LAN just for my 360 and my Windows 7 Media edition notebook to talk to each other, rather than using my current 2.4 GHz LAN that everything else uses.