pictures do not update

Hi,
I think Froogle is great,lots of hits on my items since I uploaded the
feed to Froogle.Question,I have changed my picures on my website and
uploaded a new feed using the same picture URL for both
pictures,deleting the old one on my server,yet Froogle still showes the
old picture.How can this be as the old picture no longer exists on my
server?
Second picture,how do you get a merchant rate?
Kind Regards,
Ian