Not sure what is going on but I find I cannot wifi to my HH4 with two phones; more the case that they each will only connect one way.
My Galaxy S2 will only connect via 2.4GHz and my wife's Galaxy S3 mini will only connect via 5GHz!!
I have renamed the 5GHz SSID by adding "-5GHz" to the supplied name.
BTW they both connect at 2.4GHz via an ASUS WAP attached to the HH4.
However as they both now connect some way I am not too worried.