Aside from the obvious (too much sugar = over primed and cleaning v sanitizing), there was a post on page one asking about fermentation. If fermentation isn't completed, it will continue in the bottle, thus producing CO2 on top of what the sugar will add. Plastic bucket fermentors can leach air so that it may appear to be no activity in the airlock (bubbling) even if fermentation isn't complete.
To be sure, take specific gravity reading at the end. Also, don't rush bottling, set the fermentor in a cool spot for an extra week or two before bottling. In addition to completing the fermentation the yeast will then start to clear up the beer, making the beer taste better.
For now, store your bottles in a cold place (but above freezing). The cool will reduce the air pressure. It will take longer to fully carbonate, but as mentioned, good things will happen in that cool rest before drinking.