USB Devices Disabled when no devices are connected using iMac 5K OS 10.10.3

When there are no USB devices connected to iMac, it keeps showing this.


I tried SMC resetting, booting through Safe Mode, and nothing is working to make this alert go away.

Has anyone had the same experience?
None of apple technical support instructions worked. 
Called for Apple Care Service
Technician came with a brand new mother board
Replaced and problem fixed.


So basically it was hardware failure, which can't be answered here since the board was taken.