I wouldn't recommend a third increase in speed, but if it runs stable, hell why not. However it's probably slowly frying itself.

100 to 133 should be fine, esp for AMD cpu's which are overclockers' favourites. Word of advice before you take the plunge; Make sure you can afford to shell out for a new processor and/or anything else should it go up in flames - you'd be pretty pissed if you couldn't!!