I've saved a couple boards that did the no post after overclocks by pulling the power cord, removing the battery and CMOS jumper, unseating the bios chip, and letting it sit for 10-15min then reseating the bios chip, putting everything back and holding the insert key. It didn't work the first time on either but the 2nd time each fully recovered.
I would first make certain your case power button isn't flakey by shorting the pins with a screwdriver though. Also, it's a good idea to only change a few settings at a time when in the bios and let the board boot to the desktop then reboot and change a few more, especially overclock settings. Many have nuked their bios by "going for the throat" but I've seen a great deal less of that with newer bios revisions on NF2 boards. Another cold boot issue I've seen is due to the system trying to use the default mutiplier and vcore to boot regardless of what you set in the bios and the CPU simply can't handle the resulting speed with those settings in which case pulling the power cord and battery for a minute resolved it or in some cases just turning the power switch off long enough to kill the 5v standby.