What happens to iPhoto originals in Aperture

I use both

• Aperture to store and manage my hobby photography and any pro work I do
• iPhoto to hold my family and friends snapshots (and manage my personal flickr, facebook and web gallery sites).

If I use the pro camera for any personal stuff, I process in Aperture, copy the final selections to iPhoto and remove them from Aperture.

For me, its best to separate hobby/business from pleasure.

Not sure if this will solve your problem but it might be a good starting point.

Try rebuilding the iPhoto library. You can do this by holding down the Command and Option keys while opening iPhoto. You will then need to choose the rebuild options. I think it would probably pay to select all of them. iPhoto will then work away for a long time and rebuild the library.

There is an Apple support web page that details this process further. I would normally say that you should keep a backup before making any changes like this but I guess you still have the copy of the library on the old iMac

If the rebuild doesn't help then I'm not really sure what you can do.