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.