You attempt to do a visual upgrade to a MOSS 2007 site that was upgraded to SharePoint 2010 and you get the error:
“Visual Upgrade failed. The default master page for this user interface could not be found at “/teams/xxxxx/_catalogs/masterpage/v4.master”. Add the requested master page at this path and try again.”
Troubleshoot issues with Microsoft SharePoint Foundation.
Correlation ID: a4ead41e-8c93-4d9d-ae0e-580902b71714
The problem is that SharePoint is looking for a masterpage that isn’t in the master page library. This missing masterpage is usually the v4.master page.
To add the v4.master page to the library:
1. Go to the upgraded 2010 site, and create a subsite
2. Download a copy of the v4.master page. (Site Settings > Galleries > Master Pages)
3. Go to the top level site (or any site where the error is) and upload the copy of the v4.master into the master page gallery. (Site Settings > Galleries > Master Pages)
4. Try the visual upgrade again.
Once the v4.master page is added to the master page library, the visual upgrade to the SharePoint 2010 look and feel should work.