Aperture photo recognition not very efficient

I have recently purchased aperture and was excited with all the features. I used faces on a couple of family portrait shoots which worked well.

However on returning from Egypt with around 1000 photos I am having difficulties. Ap is not recognising all the associated faces - in fact it suggests many more incorrect faces that the right ones - about 10 wrong faces to each correct one. I didn't experience this in when I used faces for the shoots. I have added a few thousand photos since but would be disappointed if this was the issue. Having used Picasa before I found never had issues recommending appropriate faces.

Can anyone help?

My workflow.

- import photos and keep originals in the pictures folder - not the aperture library

- rate them, name them, edit them

- choose faces in the inspector and I can see some faces of family at the bottom. I name a few

- I then click a face I have named to attempt to have aperture suggest appropriate faces

- Aperture thinks then displays several photos, most of which are incorrect.

- I then tried manually naming more of the same faces in the bottom section in order to see if that helps. It doesn't.

Again this all happened ok with my studio shoot but holiday pictures have not worked we'll at all - unlike Picasa which is excellent.

By the way - is there any way to have Aperture just use the current project for face recognition - I.e. it would be easier for me to only have faces from the holiday to choose from - not the entire library.

Thanks