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 !