IR won't activate screen on 10.8.3 Mountain Lion Mac Mini
Don't know how to get the display to wake up using your IR remote, but @wuc provided a great workround since you said you can ssh into the machine.  

Step 1: SSH into your Mac.

Step 2: Run this command: pmset schedule wake "01/01/2012 20:00:00" (with a date of your choosing, of course).

Here's a bit of background on the new "features" Apple added to Lion and Mountain Lion that make it harder to wake up your display.