After running multiple hours with 4 modules of 4 GB the system crashes with memory error beep code and error code 41 on the mainboard display.
Running the system with no memory the error code changes to 20.
Same result for DDR3 1066, 1333 and 1600.
The system will run with 2 modules of 4GB PC1600 in the Channel B slots without any error.
Any memory in channel A slots will cause error code 41 and memory error beep code.
After removing and reinstalling the CPU the system will work for multiple hours again before the same error returns.