If you have a Thunderbolt-equipped Mac--lucky you!--it's time to back up your data and set a little bit of time aside to download and run Thunderbolt Firmware Update v1.2, released by Apple on Thursday.
According to Apple, the update is a stability fix for Thunderbolt and Target Disk Mode. The update is a scant 1.2MB in size and requires OS X 10.8.3 or later.
If you have a Mac laptop, be sure to plug it in before you run the update. During the installation, your Mac will restart and the screen will go gray with a status indication bar.