I just installed the Apprentice version on my MacBookPro (OSX 10.6.1 + all system requirements are correct) but once I click the Houdini application icon the program won't start, basically it doesn't do anything. Does anybody know what's happening? any advice? Thanks!

it looks like there is still an issue with installer not setting up the permissions correctly.

You can manually fix it by following the steps outlined in this thread:
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=16738&postdays=0&postorder=asc&start=25 [sidefx.com]