"There is already a file with the same name..." when copying

Copying a folder containing some files and subdirectories to an empty folder
on a different partition using Vista Windows Explorer sometimes I get errors
"There is already a file with the same name in this location ...".

The problem seems to be related to permissions.

Steps to reproduce:
Create a folder \test with a file test.txt and a subdirectory \db.
Using SQL Server Management Studio create a new SQL Server 2005 SP1 database
with full-text catalog in the \db folder.

\test\test.txt
\test\db\test.mdf
\test\db\test_log.mdf
\test\db\fulltextcat\...

Shut down all SQL Server processes.
Copy \test to an empty folder.
Click continue when Explorer asks for admin permission.
Explorer complains that test.txt already exists.