Problem in showing messages

[laurab]

Some of my users have reported this problem...
They say that the screen does not refresh until they write something in the chat.
Then, when they write all the other messages appears... but every moment to refresh the screen they have to type in something.

I haven't been able to reproduce it. It works fine for me and most of the users.
I asked details to the users with the problem and they say they have Window Xp and IE8.

What can I do? What can I ask them to check?

Thank you!
Laura