java.io.IOException: Unable to delete <FOLDER_NAME> - files in dir: [<WEB_REFERENCE_FILE>]

I receive the following error when building about 90% of my builds. The other
10% it works fine. I make no changes between the times it succeeds and the
times it fails. I'm building in IE6 accessing the Hudson admin section. The
delete is occurring because it is wiping out the workspace each time; but
obviously failing.

Started by user anonymous
[workspace] $ e:\tfs\tf.exe workspaces -format:brief -
server:http://<server>:8080 ********
No workspace matching *;<USER_ID> on computer <COMPUTER_NAME> found in Team
Foundation Server http://<server>:8080.
FATAL: Unable to delete <FOLDER_NAME_IN_PROJECT> - files in dir:
<WEB_REFERENCE_FILE_IN_PROJECT>
java.io.IOException: Unable to delete <FOLDER_NAME> - files in dir:
[<WEB_REFERENCE_FILE>]
at hudson.Util.deleteFile(Util.java:218)
at hudson.Util.deleteRecursive(Util.java:251)
at hudson.Util.deleteContentsRecursive(Util.java:185)
at hudson.Util.deleteRecursive(Util.java:250)
at hudson.Util.deleteContentsRecursive(Util.java:185)
at hudson.Util.deleteRecursive(Util.java:250)
at hudson.Util.deleteContentsRecursive(Util.java:185)
at hudson.FilePath$11.invoke(FilePath.java:719)
at hudson.FilePath$11.invoke(FilePath.java:717)
at hudson.FilePath.act(FilePath.java:635)
at hudson.FilePath.deleteContents(FilePath.java:717)
at hudson.plugins.tfs.actions.CheckoutAction.checkout
(CheckoutAction.java:40)
at hudson.plugins.tfs.TeamFoundationServerScm.checkout
(TeamFoundationServerScm.java:143)
at hudson.model.AbstractProject.checkout(AbstractProject.java:830)
at hudson.model.AbstractBuild$AbstractRunner.checkout
(AbstractBuild.java:314)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:266)
at hudson.model.Run.run(Run.java:927)
at hudson.model.Build.run(Build.java:112)
at hudson.model.ResourceController.execute(ResourceController.java:93)
at hudson.model.Executor.run(Executor.java:119)