We were recently approached by a customer who had created a Windows SharePoint Services v3 site - but they also still had a v2 site.
In the process of moving documents over (in Explorer view) from WSS v2 to WSS v3, one document library began to throw this error:
"A WebPartZone can only exist on a page which contains a SPWebPartManager. The SPWebPartManager must be placed before any WebPartZones on the page."
After reviewing this further (and knowing the client had not used SharePoint Designer to modify any master pages - and only one document library was impacted) these are the steps we followed:
1) At the top level site where the document library is, go to Site Actions-> Site Settings.
2) Under Site Administration choose Site Libraries and Lists.
3) Choose the name of the list that is giving you trouble.
4) Under Views, create a new view that shows the information you want to present in the view (in our case, it was all documents so it was just a matter of choosing the columns to show in the view).
5)Make it the default view.
The customer could now view the documents in the document library.
Alternatively, you could:
-Create a new document library
-Open the site in SharePoint Desginer
-Navigate to the corrupted view (in this case, allitems.aspx) in the new document library in SharePoint Designer (found in 'Forms' under the new document library)
-Save it to your desktop
-Rename the corrupted .aspx file in the old document library
-Copy the new view off of our desktop