Thunderbolt Display shuts off on iTunes sync

This. Is an odd one. Plugged my iphone 5s into the displays USB port and then started iTunes. All was well until I chose my phone and pressed sync. When I did the Thunderbolt Display went black. MBP mid 2011 seemed to lock up totally but sync still appeared to be active. Forced restart. Anyone else ever see anything like this? I have a keyboard and a thunderbolt SSD attached. Should not be a power draw as I charge this way all the time.