Commit the directory, not the file.
Think of a directory as a text file containing the list of files it contains, then you can see that to commit successfully, you need to update the directory itself so it can remove the old entry and add the new entry. This will show up in SVN as deleting the old and adding the new file (ie 2 changes to the directory, not 1 change to the file)
If only want to commit the 1 file, you will need to add the other changed files to an ignore list temporarily.