Sounds like maybe a bad stick of ram possibly. Another thing could be the memory itself. Did you check the tested memory on evga site for your board? It's possible that maybe only 2gb of your ram will work with that board versus 4 gb of a tested brand..Well I did some digging and it isnt tested/supported. Heres the 800mhz supported memory for your board:
800 MHz(PC2 6400)
Mushkin XP6400
OCZ OCZ2G8002GK
OCZ OCZ2P800R21G
OCZ OCZ2T8002GK
Corsair XMS6405v4.1
Corsair TWIN2X2048-6400
G.Skill F2-6400PHU2-2GBHZ
G.Skill F2-6400PHU2-2GBNR
G.SKILL F2-6400CL4D-2GBPK
G.SKILL F2-6400CL5D-4GBPQ
Team Xtreem PC2-6400 800MHz 3-3-3-8
Team Xtreem PC2-6400 800MHz 4-4-4-10
Patriot PDC22G6400ELK
Geil Ultra GX22GB6400UDC
Super Talent T800UX2GC4
Here's the specs for your memory. I would check the bios to see if it is seeing it as such. If not manually set the timings and voltage. Try at 1.8 first, then if 4gb still wont boot, increase the volts to 2.0v
Voltage 1.8V - 2.0V
Timing 5-5-5-15
If that dont work, rma for evga tested memory. I've never not once had problems from Kingston or Corsair. If you dont plan on overclocking, dont buy expensive or high speed memory.
http://www.evga.com/support/mbmem/