String groups error.

at translation -> manage -> string groups

I get error when i try to download translation or upload och update translation status etc. I cannot get the strings translated because of the error messages. I have tried to reinstall wordpress but i get the same error. I have tried to start a new admin user and also to clean the chrome browser cache but i still get the same error. This is the error output:

Warning: Cannot modify header information – headers already sent by (output started at /home/matterik/public_html/matterik.com/blogg/wp-content/plugins/lingotek-translation/admin/view-manage.php:2) in /home/matterik/public_html/matterik.com/blogg/wp-includes/pluggable.php on line 1179