New release: version 3.3.0, 24th June 2013
USB3 hubs continue to be problematic with USB devices for reasons that are still unclear. Since the devices in question that are problematic are all usb1.1, if you were looking to purchase a hub and use cgminer as your primary mining platform, please go with a USB2 hub instead. The problem only manifests with multiple usb1.1 devices on the USB3 hub (i.e. all icarus based devices). If you wish to use multiple devices on a USB3 hub and cgminer, version 3.1.1 which uses the old driver model works best.
IIRC, the Block Erupters use the Icarus driver, which doesn't work with USB3.0 hubs in CGMiner.