Create another Facebook account, just to see if it works with Aperture. If the other account works fine, then the problem is likely with your existing Facebook account.
I suppose there might also be a problem with the Facebook app that's responsible for uploading images from Aperture, you might also try logging in as a different user on your machine and trying to set up your Facebook account from there.
Thanks you both for your advice. With another facebook account there is no problem. All worked fine for me, so there seems tot be a problem with my first facebook account, but i don't know what.
When i make an account in Aperture/preferences/Web i see the following message:
I have checked my facebook account a hundred times, but still no succes.
Anyone an idea?