User cannot see other user´s posts

Apparently one of my users is having troubles seeing someone else´s posts. It´s just one user she´s having problems with.
She says that she discovered it by seeing that the invisible user had posted last in a topic but when she goes to read the topic she cannot see the posts.
I asked her to see all of her posts and she says she cannot see them.
What´s going on and can this be fixed?

edit: and another one of my users cannot see people´s avatars. How can that be fixed?

Try Cleaning Cache => Here

Thanks I told them to do that. I´ll be reporting back.

Um, should be sorted.