...reset all network settings on the iPhone 4 and reboot?
I've had luck doing that on some nearby (but similar) networks.
Thinking longer term, I'd consider upgrading to a dual band 'N' (or AC) router where one (presumably, the 'guest network') resides on one band, while the second (primary use) band is for the homeowners/residents. It's a pricey upgrade now though just to get AC technology.
We have two wireless networks in our house (Just one requires a password), but sometimes lately my iPhone 4 cannot connect with either. This happens on and off through the day and night. Meanwhile my wireless Internet radio works just fine while my iPhone cannot get onto either network.
(If it matters, I leave the Internet radio on all the time because it was having trouble connecting to either wireless network. Now it seems fine.)
My hub seems to work just fine. Any ideas?
Do please pardon my total ignorance.