Clicking Exit or Attachments not working for some - any ideas?

Hello,

I have several courses hosted on our LMS, launching in a new window, all working fine...apart from a handful of users reporting that they cannot exit or download any attachments.

If they click on the Exit/Attachments the 'menu' drops down, but 'Exit now' doesn't close the window, or clicking any of the attachment names doesn't launch them.

Because the content works absolutely fine for the majority of users I'm trying to think of what particular settings are preventing it for these few. Popup blockers, clearing browser cache, updating Flash, saying 'please'.. ...nothing's worked so far.

Has anyone else had this before, or have any other ideas of what else I can check?

Louise