I have been modify a certificate to add additional lines of text. I was going along well when I started hitting the following warning:
Warning: sprintf() [function.sprintf]: Too few arguments in /home/newed3/public_html/campus/lib/moodlelib.php(5478) : eval()'d code on line 1
FPDF error: Some data has already been output to browser, can't send PDF file
I took out a few strings in the certificate.php file and the warning went away. It seems that the certificate file or language file can only handle a certain number of arguments?
More than likely, the problem was that you had extra blank spaces at the end of the lang string, or extra returns.