Hold CMD + R on startup. Do you see anything?Still no luck. I am desperate
lasniko--I fugured out the problem but no the solution.
The problem is the two thunderbolt ports. I had my monitor connected via mini display port adaptor to vga.
After the update the monitor seems dead (it is working if connected to another computer).
After connecting the mini via hdmi to another monitor everything is ok.
So my concern is what happened to the two thunderbolt ports.