We put my 2004 L300 Saturn into park, shut the engine off, then realized the green light on the gear shift was still on drive even though the gear shift was on park. Car won't start back up.
http://www.saturnfans.com/forums/showthread.php?t=173939 -- there is some talk of shifter cable issues of gm cars of around the same year model of yours. I would inspect shifter cable it's probably broke or come loose some how.
Search Saturn L300 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Saturn L300 Experts