OK, for the ones who are still looking for a solution to this problem, here it is.
Go with your FTP-program to: /domains/yoursite.com/public_html/components/com_comprofiler/plugin/language/default_language/
Overwrite the content of the default_language folder with the content for the dutch language plugin.
Rename dutch.php and dutch.xml to default_language.php and default_language.xml
DONE!!
I know, it is not the solution everyone is looking for, but it works!