Apple released Thunderbolt Firmware Update v1.2 which provides stability fixes for Thunderbolt and and Target Disk Mode.
About Thunderbolt Firmware Update v1.2
This update provides stability fixes for Thunderbolt and Target Disk Mode.
When your computer restarts a gray screen will appear with a status bar to indicate the progress of the update.
Do not disturb or shut off the power on your computer during this update. Note: Your computer must be plugged into AC power for the update to install.