Originally Posted by natedog437
I tightened each one pretty tightly until the rubber gasket was bulging out all around where it seals.
There was your mistake. Get another gasket, and don't go He-Man on it.
The torque specs for oil pan bolts is only in the neighborhood of 30 INCH LBS. If you bulge the rubber, it's over tight, the rubber's distorted, and it will leak like a do-it-yourself plumbing job.
Also, if you over tightened the pan, you run the risk of pulling the mounting holes of the pan higher than the gasket surface. The only fix for that is to take a flat hammer and knock them back down before you try again.