Apple has just released un update to the Thunderbolt firmware of the 2012 MacBook Pro, addressing issues with certain Thunderbolt cables. In some cases, this caused powered Thunderbolt USB hubs (such as the Thunderbolt Display) to have connectivity issues with USB devices.
About Thunderbolt Firmware Update v1.1 This update addresses an issue with MacBook Pro (mid 2012) and some Thunderbolt cables that may prevent bus-powered Thunderbolt devices from functioning properly.
The update weighs in at just 442KB, and is available now through Software Update on eligible Macs, as well as direct download from Apple’s support site.