I am guessing, but you may be encountering a memory problem...eg it is freaking out when it finds 4 G of memory
I would try pulling out dimms so you have (1 maybe 2G) then install the OS, then put them back in afterwards.
With linux you could probably pass mem=1024M as a kernel parameter to bypass the mem issue during install. I am thinking you should pick an "enterprise" kernel when installing fedora as that should have high memory/4G switchs alrady compiled into the kernel.
Sorry for not posting sooner. I had this exact problem and went through several replacement motherboards before discovering the solution.
On page 2-9 paragraph 1.(2) of the DK8X user manual it states:
"DIMM slots A1 and B1 are paired, and slots A2 and B2 are paired. If you are only installing two DIMMS into a Memory Bank, it is recommended that you install them in slots A1 and B1 to get the full bandwidth."
This statement is in error and produces exactly the problem you describe. The correct slots are A0 and B0.