It's been a LLLOOOOONNNNG time, but another member had an issue with this in the past and it ended up being something in the center console. I would have to dig back through past threads, but if the brake light switch doesn't solve your problem I believe there is another switch of some kind in the center console near the shifter that allows the shift lock button to be pressed in.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless