Yes, that happened to me. I found an old MacNN thread that had the answer:
Make sure you have iphoto 5.0.2 installed. If you still get nothing, apply a dummy keyword to all the photos in your iphoto library (for example 'spotlight') Spotlight should now find all your photos with whatever keywords you had previously applied to them. Now you can remove that dummy keyword from all your photos in iphoto and everyone should work great.