[TYPO3-dev] Is this a bug?

[Daniel Doesburg [netcreators]]

Hi,

In v4rc1 I get a message in the well known yellow box if I try to change 
the language of an user. It says there should be something installed in 
typo3conf/l10n.
I don't understand this.

Who can point me to the right direction?

Regards,

Daniel