strange path errors

Hi all,

I am suddenly getting path errors in my application where there were
none before. I have a user login that directs the user to their profile
page. I can login ok for some users, but others I am getting path errors
such that I cant log in e.g.

user_photo_url failed to generate from :controller=>"user_photos",
:user_id=>#<User id: 2, user_name:......

This path is in my user profile view:

1: <li>
2: <%= link_to image_tag(photo.public_filename('thumb')),
3: user_photo_path(:user_id => photo.user, :id => photo)
%>
4: </li>

Even with the users that can login, I am getting other "failed to
Generate" path errors.

Does anyone know why this would happen? The only thing I can think of is
I opened up another version of the app today (I used the same DB).