strang oc'ing occurence...

[potatoBBQ]

I have P4 2.26 @ 2.72 (17x160) @ 1.625v w/ the Corsair PC3200 running at 400 MHz on an Asus P4B533-V board which has been running great, but yesterday after I applied some Windows security patches and rebooted, it would refuse to start Windows XP (freeze on the black loading screen right after the XP logo w/ the progress bar appears) until I clocked back down to 2.26. After I was able to boot into XP @ 2.26, I tried to reboot and oc back to 2.72 but it froze again. I turned off my machine for a few minutes and the oc'ed back to 2.72 again and it works fine again. What's surprising is I've been running Prime95 for 7 hours or so with no errors and the system seems stable enough, but I can't think of an explanation of the Windows hung on that one incident. Any ideas?