Problems with PyroCMS and Subdomain

[eluser]Unknown[/eluser]
Hi Guys,

that's the first time I'm posting so at first a nice hello to all codeigniters :-P

I know this is not the pyroCMS forum, but that forum is not very useful and I suppose thats a general codeigniter thing and I don't know how to solve ...

I have installed pyrocms on a special folder in my docroot, and the important thing is: I've setup a Subdomain so the url is http://dev.mydomain.com/pyrocms/

Now, after the installation, there is an Error:

An Error Was Encountered
Die Datenbank versucht eine ungültige Konfigurationsgruppe "dev" zu nutzen.

(in english maybe: The Database is trying to use an invalid configuration group "dev")

"dev" comes from my subdomain I think. But the error message doesn't really make sense to me.

The error comes from "error_invalid_db_group".

can somebody help me please? :-)