Concur with AC, this is likely a hardware problem in the GPU logic itself (not firmware, manufacturing defect, nor OSX related). The issue appears to be very reproducible-- 5-10 minutes after wake, blank screen. The problem surfaced on Win/Linux PC's in June-- no fix from Intel in two releases of MRC code. Fast forward 5 months, Mac Mini's on OSX show same problem. No fix from Intel, no fix from Apple. So, it's not O/S, not mobo, not manufacturing, not firmware-->> it's HARDWARE related to a faulty HD4000 GPU. This issue was also present in the HD3000 GPU, and Intel still has not fixed it in the HD4000.
I worked in the chip industry as a supplier to Apple (not Intel), and every version of silicon we released had issues. The game is this: you hope your customer doesn't find out the issues that don't have a workaround in firmware, because then you start a very expensive process -> redesign the chip, spin it, test it, manufacture another run at the foundry, and fab and replace new mobo's--> a process that costs millions. Everybody remember Intel's Sandy Bridge chipset design error issue found by Tom'sHardware that Intel first tried to brush off, then was forced into a recall that cost $700MM?
http://www.notebookreview.com/default.asp?newsID=6030
Everyone is foolish to think Apple or Intel will admit this is a hardware issue because EVERY Mini out there will require a new mobo with a redesigned GPU. Intel is probably pushing Apple and the other OEM's to hold off until they can get Haswell out in the spring. Apple is in danger of becoming the Dell of the 2003-05 era, by continuing to sell faulty hardware with a known cap issue claiming their mobo's weren't affected. http://spectrum.ieee.org/tech-talk/computing/hardware/dell-tried-to-hide-bad-cap acitors-problem
If you can live with the issue, keep your Mini, but its resale value will fall when this issue becomes well-known. I returned my 2012 Mini 2.6 after 10 days and bought a 2011 refurb Mini with Radeon GPU. No problem. Wake up folks, return it, and save that hard-earned cash to buy another day. Good luck!