Parece que uma atualização da Microsoft (KB980408) causou esse problema em alguns sistemas.
“Deleting the following registry keys, and rebooting, has solved the problem for me:”
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions\{2112AB0A-C86A-4ffe-A368-0DE96E47012E}]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions\{491E922F-5643-4af4-A7EB-4E7A138D8174}]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions\{7b0db17d-9cd2-4a93-9733-46cc89022e7c}]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions\{A302545D-DEFF-464b-ABE8-61C8648D939B}]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions\{A990AE9F-A03B-4e80-94BC-9912D7504104}]