Problem with language settings in mail

Hey guys,

I've got a serious problem that needs to get resolved very fast. My WHMCS installation loads my English mail templates, instead of my Dutch templates. But, there's more...

Let me be clear, I've tried everything to resolve this bug. I've set the default language of my WHMCS back to English, to see if the problem was resolved, without any luck. Then I tried to switch the language of my emailtemplates (English <--> Dutch) to see if it fix the bug, and yes it did! Until I send an English costumer an invoice, they received it in Dutch language.

Another strange problem, is that I can't add any language below my mail templates. I do have two languages (English and Dutch), but even if I add more languages (from WHMCS itself), I can't add more languages. I guess that I have to replace the defealt language with my Dutch templates, which I've already did, and try to set the English templates into English language, not Dutch. However, I didn't found a solution to change the second language into English instead of Dutch.

Does anyone know how to fix this? Are the translated mail templates stored in the database? (if so, where?) Thanks!