It sounds like your php.ini configuration settings are preventing local files being opened. From http://uk.php.net/fopen :
If PHP has decided that filename specifies a local file, then it will try to open a stream on that file. The file must be accessible to PHP, so you need to ensure that the file access permissions allow this access. If you have enabled safe mode, or open_basedir further restrictions may apply.
If PHP has decided that filename specifies a registered protocol, and that protocol is registered as a network URL, PHP will check to make sure that allow_url_fopen is enabled. If it is switched off, PHP will emit a warning and the fopen call will fail.
Since the file being opened is not on the network, you can rule out allow_url_fopen. So things to check are firstly that if you have open_basedir set that it set to allow files in your magento directory to be opened - I’d suggest using /home/onepiece/public_html/
If that doesn’t work, and safe_mode is on, try turning it off. It’s probably on for a reason so if this does work it’s probably worth looking at how you can use magento with safe_mode on.