Then I would try to create a new library and to import your current library into the new library, if you have enough disk space for two copies of your library.
Alternatively could you try to manually repair your current library, as described in this discussion:
Before you try the second option, make sure you have a backup of your library, because you need to patch inside the package.
Thanks so much for your help. I'll try creating a new library and see what happens. Beyond that, I guess i'll try the second option, but this has been one of many, many issues I've had since getting this program.
I hate to say it, but I think I may migrate over to Lightroom (so if you have amny experience with that and have anything to say, I'd love to hear it). Nice as it is to have a program like Aperture that I understand intuitively (like a pro iPhoto), I can't rationalize it when it's full of bugs. It's a sad day if I have to escape yet another Mac program (Final Cut was the first).
I think the slowness and other issues you observe with Aperture right now, may very well all be caused by the same problem - a corruption of your library. And that can occur, if you force quit Aperture, and Aperture cannot finish the database transaction it is performing. Then the database will need repairing. Usually the First Aid tools are sufficient to deal with that, but if you force quit the program at a very unlucky moment, then the corruption can be severe.
Aperture may have some bugs - but not more than any other very complex software at that level. To you it may look differently right now, being confronted with a broken library and a very unresponsive application.
I'll sign off for tonight - in germany it's long past midnight.
I was facing a similar issue tonight. Had 13 photos in a project that wouldn't show up when I clicked on the project - BUT they would show if I placed that project inside a folder then clicked that folder. I went round in circles and search online etc until I thought to just quit and restart Aperture. Now the project is fine and all seems to be showing correctly. FYI - Maybe related but tonight software update took me to the latest version 3.3.1 and rebuilt the library.
I know it's an obvious one but I spent at least 30mins before thinking to do a simple restart!!
I had a similar problem. I was working on a project when suddenly noticed that the photos weren't showing up when I clicked on it either from the main window, or the library browser on the left. Luckily, the photos showed up just fine when I selected the exact same project from the recent menu.
From there, I just created a new project and moved the photos into it, and all is good.
My best guess is that somehow the project itself somehow got corrupted and that resulted in the problem.
Not sure if you solved this or not, but I have just had the same problem with one of my project folders...
I tried all the steps shown in the previous posts and nothing (with the exception of deleting and re-installing the application) managed to fix it.
With some fiddling and guessing I think that Ive found a fix...
1. Export the affected project to your desktop
2. Open the exported project file as a 'new' library (it still didnt show any of the images when opened from the Proects section of the sidebar, but for some reason it does show them all if you open it from the Recent section).
3. Select all the images and 'export originals' to a new folder on the desktop
4. Close the 'new' library and go back to your normal one
5. Delete the corrupted Project
6. Import the images from the exported file on the desktop into a new (replacement) Project folder