I don't know what happened, but some days after not have been on my site I had suddenly a HTTP 500 Internal Server Error

This is what the debug log (in cache dir) says:
"[18-Jul-2011 11:05:38] PHP Fatal error: Multiple access type modifiers are not allowed in /home/pulpkio/domains/pulpkiosk.net/public_html/includes/classes/ssu/cores/parser.php on line 10"

Could it be caused by third party? Everything is secured following guidelines. Please what do I have to do to reach my site?