I'm sorry for not giving you the FIRST and BEST walkthrough on this update, but I had some glitches because of my beta-testing and translating for Game Hive (that's right, it's going to be released in Swedish in the future).
Anyhow, for you still stuck and have no idea what to do in order to "beat" this last puzzle, I found a link to a walkthough. You'll find it at the end of this post.
If you want to try it yourself, want a few hints and nothing more or are afraid of clicking on strange links ... here's my way:
1. You need two keys in order to open the standard door.
2. One of them is found in the compass (not that hard to spot to be honest, it's just a bit dark though).
3. The other one is found in the clock. Use the pendulum. Hint: The cat's (@bookshelf) eye-movements represent a code.
4. Do not progress to far into the old escape-route, the candle WILL burn out. You need it to read the text once you get past the door. Hint: Turn upsidedown and learn to read 1337.
5. Middle cabinet has a purpose, and the music box is an item to reuse.
Comment if you need any help. Cheers (or just follow the link, w/e).
As promiced: http://mikediddo.blogspot.com/2010/02/antrim-escape-walkthrough-alternate.html