Since these chips have come out, there has been a regular flow of people that have been finding really low OC ceilings on these chips. If I were you, I would take the time to find these threads and check to see if there are any common parts (MB manufacturer/chipsets, memory etc).
My gut feeling is that the 785g chipset is the limiting factor, as 785g + Athlon II seems a VERY common setup, and if my memory is accurate at all, a seemingly common factor amongst those running into low FSB limits.
Try updating your Mobo bios, if it isn't already running the newest version. On my old 710 I was limited to a 225FSB for stability until I updated from the basic bios it was shipped with.
I've updated my BIOS to the latest version and am still getting pretty much the same results. I've been really gentle this time. Upping the CPU/HT Reference Clock by 1 MHz at a time. It works great at 210 (x14 = 2940 MHz), at 215 it - hangs at POST and is stuck until I restart it.
CPU: AMD Athlon II X4 630
MB: ASUS M4A785TD-M EVO
RAM: 2x 2GB Adata DDR3 1600
The memclock value was 400 out of the box and I got memory errors with that setting (no OC). I set the memclock to 667 (1333) and it works great. Try using a higher memclock value, it might be set too low.