Hi Mark,
I also had this problem, fortunately the solution is pretty simple.
You need to open YOURJOOMLAROOT/plugins/system/contentprotection.php with an editor like Dreamweaver or Notepad and remove the blank lines at the start of the file before <?php then just save and re-upload.
I have attached a fixed version of the file here.
Hi I have installed a Seminar Booking System and while working i the error attached below is this also the solution ?
Thanks padir