Acer no wifi connection

hi there.
i just bought an ACER aspire running on Vista and i am not able to connect to my livebox through wifi. I tried everything: used the wep key,press the Reg button,turn off and on the livebox.tried again and again but it still won't connect. After putting my wep key,it tries to connect and sends a message saying that my notebook is connected to the livebox but the connection to internet is not possible.has it something to do with my livebox?should i change the channel number or mac adress? i really don't know :(
help please