[Zope] Missing Temporary Folder

I have been running zope 2.9.2 (python 2.4.2, linux - CentOS 4.3) for a month or so and have just noticed that the 'Temporary Folder' option in the ZMI 'Add' list is missing. The Temporary Folder product is installed and seems ok (icon not broken) and I have another temp_folder instance which seems to be working ok (this temp_folder instances was part of an export from an old version of zope - 2.6.1 - and which was then then imported into my current zope installation). I copied/pasted the existing temp_folder to create a new instance and that seemed to work ok as well. Does anyone have any ideas as to why 'Temporary Folder' would not appear in the 'Add' list? Thanks, Jonathan