iPhoto shared library problem

We are new apple users.

On my wife's Mac Mini, we set up a shared directory for photos. When my wife is logged in, she can open iPhoto and everything works fine, it goes to the correct shared directory of 5000 photos.

When I log in, I had iPhoto set up (by genius bar) to allow me to use the same shared directory of photos, and all was well for a couple of weeks. Something happened (no idea what). Now when I try to open iPhoto to that shared directory, I get an endless spinning wheel and have to quit iPhoto. If I open iPhoto while holding down the option key and select a different directory (my user photo library, which has just a couple of pictures in it for testing purposes) iPhoto works fine for me.

I thought it might be a permissions problem / screwup, but using the disc utility to repair permissions did not change any result - I still get the spinning wheel, she gets to the library just fine.

Suggestions?