I am still having the same problem (I have (un)install the EyeX Engine and USB 3.0 drivers lots of times).
I am running a Windows 8.1 (64) and the os automatically installs ASMedia USB 3.0 drivers (21/08/2013 version 6.3.9600.16384). When I connect the EyeX using that configuration, it allows me to start the calibration. Once the yellow dot appears the process hangs and a dialog says:
Calibration error: The calibration could not perform. Please check that your ET is plugged in and retry.
I updated the ASMedia driver as suggested earlier in this thread. Now I am using ASMedia XHCI Controllers (10.04.2014 Version 22.214.171.124). The last version. The error is exactly the same as before. It hangs when I try to do the calibration.
Finally, I downloaded the libusb-1.0.dll (also as suggested earlier in this thread), and replaced it in C:\Program Files(x86)\Tobii\Service. The error is different: the EyeX stuck on Initializing.
The EyeX device and cable are ok, I tried them in another computer.
I am enclosing the log zip file generated by the last EyeX Engine.
corresponds to the log when error 2 happens (the EyeX stuck on Initialising)
corresponds to the log when error 1 happens (error during the calibration process).