Insomniac and Russ - thanks! Bugs fixed in the copy at the above link as of now.
Mike - after seeing your description of your setup, its got to be a file permissions problem. The web server user must have write permission on the directory where the files are stored. In your case, the files are in a public_html directory. This is probably owned by your user, rather than the web server user. You need to figure out a way to give the web server write permission. The simplest way (although not good in steady-state, its a security hole) is to make the directory (not just the files in the directory) be world-writable. A better way is to use groups to do this.
For example, for the web server I am running (ubuntu linux running apache2), the web server user is www-data. So that user has to have write permission on the directory the files are contained in.
HTH,
Dave