If all DCs are GCs and in a single domain environment it doesn't matter
See bullet 1 here:
http://adisfun.blogspot.com/2009/04/lessons-learned-from-eric-fleischman.html
I wonder if you are running into a classic race condition (that is why I'd look at the logs). Can you point it to another box as primary and itself as secondary and see if that helps the next time you reboot.
Thanks
Mike