please help me with wifi :(

[belese]

-2 indicates it receive a argument that doesn't match to xbian-config.
xbmc call this function when connecting :

xbian-config network credentials wlan0 WPA myssid mykey

that's why space in not allowed now.
Post the log, or look at the log which parameter is bad, normally all xbian-config call is log (if i remember, you have to activate debug in xbmc).

or try manuall with ssh and call to xbian-config network credentials ...(with sudo).