I have seen people complaining about when you import aperture photos into iPhoto, some changes are made to the aperture library. You are going to be asked to update, afterwards causing that aperture can't open the library.
Further the structure of the aperture library should not have been maintained in iPhoto.
Just a warning so far without i have personal experiences.
Are you sure this is with Aperture 3.5 and iPhoto? Prior to Aperture 3.5 the new iPhoto did update the Library such that Aperture 3.4.5 and before could not use it. I think the update to Aperture 3.5 resolves that.
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