Sometimes you have got to love SharePoint, or more importantly love the developers who developed SharePoint to return an exception message such as “An unknown error occured” when something bad happens.
This message occurred when using the Site Actions->Manage Content and Structure feature.
After some investigation a couple of posts on MSDN were found these talked about checking various xml files which customise the Publishing Editing Toolbar and Site Actions toolbar.
The MSDN post said to check that the files were both checked in and published.
However, this did not fix the problem. After further investigation I could see that some lists had two entries in the View All Site Content page (/_layouts/viewlsts.aspx), both which linked to the same list. So the problem is how can we get rid of one of these links?
The first idea was to backup the list as a list template and then delete the list, however this would change the list id when a new list was created from the template.
Instead I had the idea to use the recycle bin feature to bring the list back.
Deleting and restoring the list from the recycle bin did indeed fix the duplicate list links and also fixed the Manage Content and Structure feature!
Next, is to workout why these list entries are duplicated.