Ran into this issue where the section on the main page called Recently Updated was not updating.

The solution was to go into Administration -> Content Indexing and Rebuild the Index.

The official instructions for Confluence is that if that does not work, then remove the <confluence-home>/index directory, restart the application server and then rebuild the index.

http://confluence.atlassian.com/display/CONF27/Rebuild+index+from+scratch