Just try it with the Asrock G41C-GS. It should work out of the box with that Xeon but I would use a BIOS with the latest microcodes.
There I patched that one already:
G41CGS_-Xeon5400-1.40.zip 666k .zip file
I think both of your G41 boards should be about the same. You could try to OC but I am not sure what options you have there for the boards. As far as I know there are very limited OC options for the G31 and G41 chipset boards so you may find yourself stuck at a very low or no OC because you are missing some voltage or frequency settings in BIOS.
Just saw this. I swapped over to the ASrock board. Still having issues. I booted with the e6700 first and patched the BIOS. Then I noticed the NB heatsink was 65C so I had to swap on one with a fan. Now that I have the NB down to 35C, with the Xeon in it becomes unstable. However I am inclined to think it might be my RAM. I've been running it for a couple years at 1173 MHz, but it's Kingston HyperX DDR3-1333 so it should be able to handle it. Now whenever I boost the RAM to 1333, I get some freezing and kernel panics/dumps.
However, memtest86+ runs fine continuously without issues. (Where is the ripping your hair out smiley?)