My MacBook Prop (late 2011) has worked just fine on my Thunderbolt Display since I installed Yosemite since day 1 and starting yesterday it stopped. When I sya it stopped working I mean the following: Display is black MacBook Pro does recognizes it The FaceTime camera still works The USB and network cable still works The power cable still works Bypassing the Tunderbolt Displays cable with my own Thunderbolt cable does exactly the same thing I don't see ghosting, but I do see ghosting on my iMac I would assume it with was my Thunderbolt Display, but it actually stopped working on my 27" iMac (2014) used as an external display using a Thunderbold cable since i installed Yosemite. The iMac as external display worked fine with Mavericks. IF I connect my MBP to my Dell Display using a DisplayPort to DVI cable, it works just fine. Any idea? Hope I gave all my details! Thanks!