[Zope] links stopped working

I have just noticed something peculiar with my Zope application. All relative links have stopped working properly and are now referring to the directory above, and therefore failing to find the correct page. eg. /folder1/folder2/folder3/dtmlmethod if i use the relative link "dtmlmethod" in folder3 i get the following error message: cannot find /folder1/folder2/dtmlmethod Has anyone seen this before? I can correct it by using absolute references but I have many such links and they should work as they have been doing. regards garry