Thanks for your reply! I've done that, just in case (i have two wrist straps, heh).
I've got a GA-Z77X-UD5H Z77 from Gigabyte, I have the large power connection plugged into the board, my video card plugged in (with it's own power connector), and all that is routed to my Corsair AX750 PSU. When I turn the PSU on, the board's power light turns on, but when I press it, the fans spin on the CPU heatsink and the PSU but then they all stop spinning (the power light on the board is still on, though).
Very strange. I'm going to go read the manual again to be sure I didn't miss anything, but I'm pretty sure it didn't say anything about this, lol.