Yeah it looks like your site has been hacked with r57shell.php
I suggest you put your site into maintenance mode.
Look in your FTP root for a file named r57shell.php and also text files with names like c.txt or something like std.c
Here is more info from symantec regarding the PHP.RSTBackdoor r57shell.php http://www.symantec.com/security_response/writeup.jsp?docid=2005-071322-4217-99&tabid=2
What is your site link please? What Version of PHPFusion are you running? What Infusions do you ave installed?
Merged on Jun 29 2011 at 10:02:01: Ok, I finally got this solved, so I figured I would post what I found out on here in case anyone else has this problem in the future. I turned in a trouble ticket with my web host asking if there was a search or anything to try and find the files mentioned above. When the tech replied he said that their security flagged the Panel_editor.php file as a security risk and that is why it showed the r57shell.php error on my error logs. He removed the flag and now it works perfectly...