I just clean installed 10.11.1 using USB drive and this guide http://osxdaily.com/2015/10/01/clean-install-os-x-el-capitan-mac/ on a mid-2015 rMBP with discrete card When I log-in, it's strange. I press the power button, then there is the black screen with the white apple. Then log-in screen. I log-in with the El Cap background, then when the progress bar reaches about half-way, the screen goes back to black page with white apple before finishing the log-in process and landing me on the desktop. Is this normal with El Cap to switch screens during the log-in process?