GB 3 refuses to inst. ! (macbook)

Hi!

I have tried 4 times now to inst. GB 3 on my macbook.
Choosing custom inst. , ONLY the GB 3 package. Repairing
permissions all the time - and removing all the garageband stuff
between every inst. attempt.
The inst. fails after the loops are installed, just after the instruments
starts to inst. Message: "there where errors installing the software"
( i have read quite a few posts about this - no help to find )
Really need help!

Regards, Toggen