BIG potential problem...Overflow leaking.

[Son Of Skyline]

I just turned off my main return pump to fish out a blenny in my overflow and a minute later I was greeted by the sound of water spilling. By the time I got down from the stool and opened up the stand doors, the sump was overflowing and the water level in my tank was dropping fast! I've had nothing but problems with this overflow from the beginning :x

It leaked from the beginning when I initially tested the tank, but I loaded the edges with silicone, tested again, patched it up some more, and it seemed to do the trick for awhile. Now it's not holding anything and the tank is just getting established.

Any suggestions on a solution besides tearing the entire tank down to fix it? Any info would be greatly appreciated, as right now if the power goes out, which has been known to happen in my house, my tank and everything around it is doomed. Thanks in advance and sorry for the long post.