admin Tags panel got 404

when I try to open Tags panel in admin (admin/tags), got 404: Page Not Found. I don't see any error, and all other pages are working fine.
Omeka 1.5.1, thanks.

Try this: follow the instructions on retrieving error messages.

You'll want the "Display Error Messages" > "Omeka 1.5" sub-section. Make sure to do both steps, including setting debug.exceptions.

After that, going to admin/tags should give a detailed message instead of the simple 404. If you post that detailed error here, we should be able to tell what's going wrong there.