You may want to drop your multiplier and try increasing your base clock... you can lower your ram clock multiplier in order to eliminate your ram OC as the issue. you will want to eliminate the number of variables you change at a time though in order to specify the problem you are running into. i would guess that dropping to a 21x multiplier then slowly increasing your Bclock until you cant boot. then increase voltage a little and see if you boot. then do the Bclock again... as tedious as that may seem it is a good way to make sure you know what your issue is with every overclock.