Error when creating patch - 1.6.3

I believe I have the latest released version (1.6.3 build 16613). I am getting a "Directory name is invalid" error message when trying to create a patch containing changes to 2 files and one new file. I've attached a snapshot of the error dialog.

To get this error, I modified two files in a project and added one new file. I right-clicked on the JGnash2 directory in my Explorer window (D:\dev\eclipse-workspaces\java\JGnash2) and chose "TortoiseSVN -> Create Patch". I checked that the 3 files I wanted in the patch were selected and clicked OK. At the "Save As" dialog, I navigated up one directory level (to "D:\dev\eclipse-workspaces\java") and specified a filename "YahooAusParser.patch") and clicked OK and then the error message appeared.

If I remove the offending file name from the list of paths in the "Create Patch" dialog, I get the same error for the next file in the list.

I've successfully run Cleanup on this directory several times but this hasn't resolved the problem.