I have had a similar problem in that the install icon flashes for a nano-second on the dock but will not install iworks 06 or ilife 06. Called Apple care and they were not very helpful. So they advised me to go to the New Brent cross store with my imac G5 and let them sort it out. So I made the long trip (62 miles) on a Friday to Apple store at Brent cross at 10 a/m, only to find the store didnt open until Saturday
So I thought now I am in London I may as well get on a tube at visit Regent street. The only slot they has was 8:45 PM.
So I told them I want my money back, why they asked, so I explained the situation. They managed to get me in at 3pm. Only to be told I had to re-install and delete all previous items.
Why couldnt applecare have told me that so I ddint have to lump my g5 about and waste a day.
Still haven't installed it, and discovered in keynote you still cant have more than one audio item like you do in imovie. Also is there an option to export a keynote presentation to DVD and play it on the a DVD player????.