TSVN Diff asserts working base to be empty

I have the file "TestData.java" in my NetBeans project.
- Doing svn-diff from Netbeans returns in 'no difference between working
copy and repository'.
- In the Windows Explorer this file (and the whole folder) are marked
red with white "!"
- DoingTortoise-diff from Windows Explorer, working base is asserted to
be empty. See attachment.
- opening "TestData.java" from the Tortoise repository browser shows the
file with the same content than the working copy
  --> so it can't be empty, but I don't find out, how to get a green
badge in the Windows Explorer for this and the other files.

Please CC your answer directly to my e-mail, because I'm not subscriber
of this list.

Regards,
Ulf

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