AOpen AX4F-4DN Motherboard Memory Restriction

Hey guys!!! I'm looking for some help here.
I just got an AOpen AX4F-4DN motherboard and I have two 512 memory sticks that I want to use with it. But when I check what memory I have it is only showing that it is using only 512.
I have tried switching which slots I put the memory in but with no luck it still shows 512 and not 1g +.
I found another post where someone was having the same problem:
http://forums.extremeoverclocking.com/t163413.html
but no solution to this problem was posted.

Please help. Thanx in advance...