Certain bottles or even whole batches of your beer may at times become over gassed, while not necessarily exploding. This can be caused by bottling to early, as the beer is still fermenting it will continue to do so in the bottle and can cause over gassing (if bottled much to early these bottles could explode).
Always use a hydrometer to be sure your beer is ready to bottle. Another cause could be infection (if the beer taste bad you will know that is the reason), make sure to clean and sterilise everything thoroughly before use. Lastly this could be caused from putting too much carbonation sugar into the bottles, using a sugar measure or carbonation drops will help make sure you are accurately carbonating each bottle.
You can put the over gassed bottles into the freezer and cool them right down to near freezing, then keep in the refrigerator, this can sometimes help! Or other people choose to uncap and re seal their bottles to let out some of the pressure, although this does pose some risk if infection due to exposure to oxygen.