I have read the FAQ and the sticky's in this area.
Still, for some reason my Messenger Plus will not work with my 2009 at the moment. Is this due the fact I am using a "hacked" version to use 2009? Or are there any other things I should think off.
If the "hacked" version of WLM is just a changed version number then yes, this is probably why. See the instructions here to keep WLM 2009 without breaking compatibility with Plus!