The same problem. DH77KC (last bios), Intel SSD 520 on SATA3 (last firmware). >30 seconds before realy booting started - HDD led blinking, but title INTEL logo with F1, F2 and F10 descriptions are shown. Sometimes the screen flashes and it is waiting for another 30s. Press F2, F10 and still waiting. After 30s period it boot normaly or skip to BIOS or boot settings (when i prees F10 or F2 key)
Now I don't turn off the PC with shutdown, but with sleep.