Did you use Genuine Toyota gaskets? I didn't use any sealer on mine and no leaks.

Maybe you have some rough spots or tiny grooves in your sealing surfaces of your cases. If that's the case, you're going to need some sealer like emsvitil mentioned. It shouldn't take much.

Sucks to have to pull it again. If you don't, you know it's going to drive you crazy. At least it wil go quicker the second time.

Wipe the surfaces with some brake clean and knock down any high spots you feel with a file. The sealer should handle the low spots.