If you do pull the pan and change the gasket as SO suggested, look at the bolt holes on the pan, you will see they are pulled up when the bolts were last tightened. You need to put the bottom side on a piece of steel to where it covers the bolt hole from the bottom, then take a small hammer and tap the lip around the bolt hole down so it is flat with the pan lip again.
When you put everything back together, the pan will draw up evenly and not leak if done correctly. Course the Titanic was claimed to be totally unsinkable, and it sank on it's first trip...
Lot of help I am eh?