(Solved) Setting a Static IP

[Darth.Severus]

Hi, I'm new. I write here, cause I think to have the same problem.

Software
XBian version: XBian 1.0 Release Candidate 3, downloaded two days ago
Overclock settings: Standard, nothing changed

Hardware
RPi model: B/512
Power supply rating: Didn't find that value. Does xbian need more power than raspian?
SD card size and make/type: 8GB Toshiba
Network (wireless or LAN): LAN
Connected devices (TV, USB, network storage, etc.):

Problem description and so on:
I can't get nor set an IP for ssh!
My Xbian is NOT connected to some router, all discussions I found are always mentioning some router. But in Linux you can set your IP without having a router. dhcp deamon or static. It's simply not working in xbian. I can't set my IP in the gui, nor in xbian-config, nor in the shell.

192.168.42.42
255.255.255.0
evtl. Gateway 192.168.42.0

gui: unexpexted error occured
xbian-config: I currently don't remember the error message
shell (../interfaces): noting after restart
Same works well with raspian. Didn't test other IPs cause I got to frustrated about it yesterday.