+1, I agree on a bad tank of gas. I had a similar situation with a CEL in Kansas after I filled up one tank with E-85 ethanol and got a CEL shorty after. At the next gas station I cleared the code and filled up the VX with premium... the CEL never came back. That happened during the middle of a 1200 mile road trip, so I'm pretty sure it was the gas.

Then again, its not a bad idea to check your spark plugs just in case.