Problem with installation of Contao 3, reason:Danish browser

I've installed quite a few typolight/contao-systems the last 3+ years - thank you, Leo, and all you supporting guys for making this great CMS!!!
So I got very frustrated yesterday, when I tried to install 3.0.6.
Lots and lots of php-warnings around the first install-window:
"Too few arguments in contao/install.php..."
"…cannot modify header information - headers already send by…" and many more - and after putting in a new password and hitting "save password", there came the "couldn't find page"-browser-error.

Earlier there could be some issues when the language-modul wasn't up to date, but I've read that from Contao 3 everything should be in the core…

Eventually I tried to change the language of my (mac-)computer and browser from Danish to English - that SOLVED the problem instantly.

So if anybody else has this install-problem, try changing the language.

And if anybody can explain why this is a problem, please let me know :)

It's a known issues and hasn't disappeared.
I read a user who had the same problem with spanish language. I've had a client with issues on a windows machine under danish.

additional ways to solve the issue are:
A) If available, download the browser in english language version (your OS system language can still be any other language)
or
B) Delete or rename the problem language folder path ROOT/system/modules/core/languages/ (the CMS will default to english)