At 350MHz your sticks are probably drawing at least 8W, so 5V 1.6A
There aren't a lot of hubs comfortable with that kind of draw without modification. It's probably an issue with voltage drop between the power brick and the USB jack itself. If you want to do any kind of really-pushing-it overclocking, you definitely want one of those plug-in USB power meters. That'll tell you a lot about what's going on.
Ok, thanks for the input. I just purchased one of those USB power meters like Jake36 recommended below.
I've seen some people mention here USB Y-Splitters (something like
this?) If I plugged the power side into say a 2.1amp phone charger, and the data side into a USB hub, would that work to supply the power needed and allow for running at the 350MHz range? Or do I need to make other modifications to allow the Y-Splitter to work?