Gradebook

When I tried to export the grades to excel or text format I get the following errors:

Download in Excel format:
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Warning: Cannot modify header information - headers already sent by (output started at /home/puchorg/public_html/course/lang/en/quiz.php:459) in /home/puchorg/public_html/course/grade/lib.php on line 1215

Warning: Cannot modify header information - headers already sent by (output started at /home/puchorg/public_html/course/lang/en/quiz.php:459) in /home/puchorg/public_html/course/grade/lib.php on line 1216

Warning: Cannot modify header information - headers already sent by (output started at /home/puchorg/public_html/course/lang/en/quiz.php:459) in /home/puchorg/public_html/course/grade/lib.php on line 1217

Warning: Cannot modify header information - headers already sent by (output started at /home/puchorg/public_html/course/lang/en/quiz.php:459) in /home/puchorg/public_html/course/grade/lib.php on line 1218
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Download in Text format:
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Warning: Cannot modify header information - headers already sent by (output started at /home/puchorg/public_html/course/lang/en/quiz.php:459) in /home/puchorg/public_html/course/grade/lib.php on line 1277
First name Surname ID number Institution Department Email address Forum: CHEM441 - Assignment: Sessional Examination 1 - Max: 30 Quiz: Quiz No.1: Properties of gases - Max: 10 Assignment: Assignment No.1 - Max: 10 Assignment: Sessional Examination 2 - Max: 30 Assignment: Sessional Examination III - Max: 30 Total sharmil Angalane sar_sen@yahoo.co.in 8 10 12 30 rambabu bandaru rambabu_bandaru1947@yahoo.co.in 1 7 8 6 19 41 venkat battula catchme_johnny@yahoo.co.in 10 4 8 8 21 51 latha bellamkonda latha_mscche@yahoo.co.in 8 7 8 11 27 61

I searched the forum, but I could not get any solution.

Can somebody suggest a solution to this problem.

thankyou in advance