Hi Mary, Thanks for your response, but that's not what I mean.
I've just installed release 2.4.1 and it's solved so no problem anymore, but this is what was happening. When opening a resource (Page/File/Url) in a popup/new it showed an extra page before showing the actual resource. In fact, it even opened an extra window after clicking on the resource link:
After upgrading to Moodle release 2.4.1 it goes straight to the resource without showing this page first.