Email notification in wrong languages

Since my upgrade from 3.0.5 to 3.0.6 I have a problem with notification mails. They should be in the language the user has set in his UCP, but apparently all users get the mails in the language, that was requestet first. So topic reply notifications are in greek, pm notifications are in english, ...
I've got 8 different languages installed in my forum.

What I've tried so far:

• Deleted greek translation
• Refreshed all style templates
• mysql command: DELETE FROM `phpbb_styles_template_data` WHERE `template_filename` LIKE '%.txt';

But still no change. I would be satisfied if I could at least get all mails in english (my forum default language is english, too)