The reason that you received this error is that you still have your local copy of the file in your working copy.
In order to include your new file in the patch you likely ran the svn add command so that the svn diff command would include the new file in the patch. If your patch is committed to the code base and you run an svn update, then you might receive an error message of: "svn: Failed to add file 'my.new.file': object of the same name already exists". The steps to correct this problem are: 1. Run the svn revert command to remove the scheduled add within Subversion. 2. Delete the file or move it to a location outside your working copy. 3. Now you should be able to run the svn update command.
You might want to compare the new file from the repository with your original file.