Same behaviour as CONF-5243 but in Confluence 3.1.2:

When you move a page (with descendents) to the part of a hierarchy in another space, the ancestors table is not correctly updated, which leads to the corruption of the hierarchy data throughout the app (at least until the ancestors table is rebuilt.)

Unfortunately this is not easily replicate-able and affects only certain instances.

If the page you are trying to move has this problem and it has an attachment, page move will fail with FileNotFound not found exception. See relevant KB article.

2010-03-29 20:52:08,066  ERROR [http-8310-1] [pages.persistence.dao.UpdateAttachmentsOnFilesystemOnPageMoveListener] moveAttachments Could not move the attachment data along with the page for move of page Solaris Tomcat install
 -- referer: http://localhost:8310/display/IT/Solaris+Tomcat+install | url: /pages/movepage.action | userName: confadm | action: movepage
java.io.FileNotFoundException: Source 'C:\confluence\confluence-home\attachments\ver003\27\117\1867777\67\243\5243067' does not exist
    at org.apache.commons.io.FileUtils.moveDirectory(FileUtils.java:1733)5243067

If you encounter this issue, please contact support and submit your space XML backup to allow us analyse the data.