Optimizing error with Mac and PC CS3

I get this message when I try to optimize a particular file:

an error was encountered while optimizing content streams.

I get it when I use a mac or pc. I've optimized other files just fine. It just happens with one file. It's 72 MB with a lot of very over-sized photos -- 95% of the size is photos! It's someone else's presentation from a conference.

I've searched everywhere and can't find a clue. I don't want to have to go in and reduce the size on all of the photos individually. Er.

Thanks!