You connect via ethernet -> antenna. Can you give us details of your connection equipment such as device names & model numbers. It seems you haven't been able to connect since you changed ISP & to a antenna connection right? So probably one or both are to blame for the problems. BTW I explained in a previous thread what to do if the installer refuses to install. There's also other options.

Sorry for late reply. I just got the info.
1/ Type Connection : Wireless 2.4Ghz, 32kbps sharing bandwidth
2/ The connection is received by Wireless Access Point which we installed with the antenna and directly goes to the computer.
The acess point model: SENAO 2611CB3 PLUS, 2.4 GHz 802.11b
The router in Base station (my provider): PC Router with OpenBSD system v3.8.
3/ ISP: CITRA

I didn't make any change on the Mac it self and Safari or Firefox goes online wihout problem. Only LimeWire says is blocked by a Firewall. Which normally souldn't be, Sharing Pref. Firewall allow him !