Have you taken apart the hub to look at the workmanship? Where was the power cord soldered to? Is the Pi being powered from the hub internally?! It could be a lot of things. Take it apart and post up some photos and we can try to help diagnose.

I have a fairly basic problem and it's the USB cable. Before I found this thread I watched a Youtube vid which advised to trim the tail. I did so but just could not get it trimmed enough to fit. I kept cutting but got scared when the black rubber started revealing clear plastic stuff. Anyway, I squeezed the whole lot in there, re-assembled and it worked somehow!!