For some days my avatar links are broken

Hi There,

For some days all my avatars links for users and blogs are broken. I can upload avatars, but I only see a broken link. During these days I updated and installed some plugins, but deactivated most of them without change.

The link from the broken avatar images is:
http://my-domain.com/avatar/user-1-96.png
The link that would work is:
http://my-domain.com/wp-content/uploads/avatars/user/c4c/user-1-96.png

As I am digging in the dark I wonder if you have any hint for me what to do?

Thanks
Tee