[Zope] Version still active after closing

Hi I have a problem with the version mechanism. I created a version object, start working on it, the day after I saved the changes and closed it. But some objects -not all- are still blocked and showing the red diamond, saying that they are currently in a version. If I open the version again, the changes I made are still there, but when I close it again, the objects still show the mark. What can I do? Gabriel Genellina Softlab SRL