Open the Console in the Utilities folder. On the left side of the window there's some "Log files." The Install Log file will be there somewhere.
Ok, I found it. Here it is:
01/03/14 11:03:18 - Starting MultiBeast 6.0.1-20131109
01/03/14 11:04:25 - Starting MultiBeast 6.0.1-20131109
01/03/14 11:08:52 - Installing 'Drivers > Audio > Realtek ALCxxx > With DSDT > ALC889'
01/03/14 11:11:34 - Installing 'Drivers > Disk > 3rd Party SATA'
01/03/14 11:12:04 - Installing 'Drivers > Misc > FakeSMC v5.3.820'
01/03/14 11:15:30 - Install of '/Users/tiziana/Desktop/MultiBeast.app/Contents/Resources/FakeSMC-v5.3.820.pkg' failed.
'installer: Package name is FakeSMC-v5.3.820
installer: Installing at base path /
installer: The install failed (Installer ha incontrato un errore che ha impedito l'installazione. Contatta il produttore del software per ottenere assistenza.)
'. Exiting.
01/03/14 11:16:57 - Starting MultiBeast 6.0.1-20131109
01/03/14 11:21:28 - Installing 'Drivers > Audio > Realtek ALCxxx > With DSDT > ALC889'
01/03/14 11:23:24 - Install of '/Users/tiziana/Desktop/MultiBeast.app/Contents/Resources/AppleHDA-10.9.0-889.pkg' failed.
'installer: Package name is AppleHDA-10.9.0-889
installer: Upgrading at base path /
installer: The upgrade failed (Installer ha incontrato un errore che ha impedito l'installazione. Contatta il produttore del software per ottenere assistenza.)
'. Exiting.
01/03/14 12:13:05 - Starting MultiBeast 6.0.1-20131109
01/03/14 12:14:24 - Installing 'Drivers > Audio > Realtek ALCxxx > With DSDT > ALC889'
01/03/14 12:16:41 - Install of '/Users/tiziana/Desktop/MultiBeast.app/Contents/Resources/AppleHDA-10.9.0-889.pkg' failed.
'installer: Package name is AppleHDA-10.9.0-889
installer: Upgrading at base path /
installer: The upgrade failed (Installer ha incontrato un errore che ha impedito l'installazione. Contatta il produttore del software per ottenere assistenza.)
'. Exiting.
01/03/14 14:00:56 - Starting MultiBeast 6.0.1-20131109
01/03/14 14:01:48 - Installing 'Drivers > Audio > Realtek ALCxxx > With DSDT > ALC889'
01/03/14 14:03:14 - Install of '/Users/tiziana/Desktop/MultiBeast.app/Contents/Resources/AppleHDA-10.9.0-889.pkg' failed.
'installer: Package name is AppleHDA-10.9.0-889
installer: Upgrading at base path /
installer: The upgrade failed (Installer ha incontrato un errore che ha impedito l'installazione. Contatta il produttore del software per ottenere assistenza.)
'. Exiting.
01/04/14 12:38:13 - Starting MultiBeast 6.0.1-20131109
01/04/14 12:38:55 - Installing 'Drivers > Audio > Realtek ALCxxx > With DSDT > ALC889'
01/04/14 12:40:43 - Install of '/Users/tiziana/Desktop/MultiBeast.app/Contents/Resources/AppleHDA-10.9.0-889.pkg' failed.
'installer: Package name is AppleHDA-10.9.0-889
installer: Upgrading at base path /
installer: The upgrade failed (Installer ha incontrato un errore che ha impedito l'installazione. Contatta il produttore del software per ottenere assistenza.)
'. Exiting.
It seems that the AppleHDA failed.