Major Oil leak / loss after oil change

[athensbenz]

Just purchased an '85 300 D Turbo and completed what I thought was a routine oil change. I let the car drain for quite some time. Last night, I put the oil back in. When I started the vehicle this morning it fired right up and sounded fine. I walked inside for 2 to 3 minutes, came back out and looked under the car only to see quite a bit of oil on the garage floor! I immediately shut the car off. From what I could tell, it was coming from the rear part of the engine.

Prior to this oil change, the oil did not even drip on the carport. Any ideas on what may have happened? I have changed the cannister filters on 240's, 300 D and SD at least 100 times with no problems.