There's a known (on the net) issue with hwclock accessing /dev/rtc causing hangs on ASUS motherboards (A7V133 in this case). To get around this, CLOCKFLAGS needs --directisa added to it for those motherboards. hwclock is called both in /etc/rc.d/sysinit and /etc/rc0.d/S01halt .. Without it, the system will seemingly hang on startup or shutdown for no reason.. I've logged this against util-linux as that's where hwclock is from, but this may be an issue with /dev/rtc in the kernel..
There's no way to reasonably know that this flag needs adding... I will ask the kernel people if this is a problem of theirs (which I would guess it is) - otherwise, you are probably stuck with just editing initscripts manually :(
I had the same problem. It occurred every time I did a normal shutdown (not reboot). To fix it, I replaced hwclock with the latest version and it seem to fix the problem... I am now using hwclock 2.15 and I don't have this problem anymore...
*** This bug has been marked as a duplicate of 34374 ***