Found a solution for me!
The last step to delay XBMC was apparently an important one.
These are all the steps I followed, explained by a noob in a noobish way. Don't know if ALL the steps are necessary, but they can't harm your system. Special thanks to
KillerBob and
winestock.
1) Update your version of OSX to the latest updates
(I mean update your version, not upgrade to another version). This was important for me, because iTunes kept opening randomly by itself in OSX 10.7.2.
2) Uncheck "Restore windows when quitting" (OSX->System Preferences/General) and/or uncheck the "Reopen windows when logging back in" checkbox in the restart or shutdown verification dialog.
3) Remove iTunes and other programs that may control the remote in login menu (OSX->System Preferences/Users & Groups/"username"/Login).
4) Make sure your remotes (Harmony, Apple, or otherwise) are NOT paired in OSX (OSX->System Preferences/Security & Privacy/General) and ensure the IR receiver is on.
5) Make sure iTunes is not paired with any of your remotes (iTunes/Preferences/Devices).
6) Install Candelair.
7a) Use the script provided by
winestock to delay start of xbmc after boot OR
7b) Install DelayedLauncher for Mac -> put XBMC in DelayedLauncher -> put DelayedLauncher in login items (OSX->System Preferences/Users & Groups/"username"/Login).
For me: to delay XBMC with 1 sec is enough, cause DelayedLauncher needs 2 sec to start on its own... so 3 sec.
8) Setup XBMC for the correct remote, Harmony or Apple.
Apparently the core-problem of not working correctly:
XBMC starts up to fast (There's a punch line!)