VOSTRO 1710 recognizes my router, connects to it but no connection

Hi,

I've a Dell VOSTRO 1710. When I use an ethernet connection with my router, there is no problem. But when I try to have a wireless connection, all the wireless network of mine and of my neighbors are recognized, my WPA password too. Vista (32 bits) says I am connected but, when I try to reach a page on the web, get my e-mails or even ping an IP, I get no response. Note that I have other devices connected to that router which works without problem. I thought it was the driver of my Wifi card (Intel 4965agn) that does not work. Thus, I try to update (and even downgrade) them from Intel® Wireless WiFi Link 4965AGN - Download Center. Nevertheless, it does not work. Note that it worked one week ago. The problem has suddenly appeared.

Thank you for your help!

Phil

(PS : I am not a native english speaker. Thank you for your comprehension of my mistakes.)