No Wifi on Ubuntu but wireless lan is connected and G.Card problem

Hi,
Hope you pepl wud b fine.
Few weeks ago I purchased a HP Pavilion dv4 1131TX laptop. I installed Ubuntu on it with vista as dual boot. Now, in Ubuntu,everything works fine except:

1. Minor Problem: I couldn't enable appearence effects. It asks to enable some extra nVidia driver.I try to enable it but it doesnt enables.

2. When Ubuntu is booted completely I can see the wireless netwrok connected in top right corner. Its connected to my college's wifi network. In my college,after connecting to the wireless network, to access the internet,we need to open any website,for the first time every session, a login page appears.There we need to login. It works completely fine in Vista.But in Ubuntu when I try to open any website in FF immediately Address Not Found error comes instead of the login page. FF behaves as if there is no network connection at all.

Please highlight what could be the possible reasons and how to fix it.

Thanks in advance.
Regards,
Aki

1) Run System->Administration->Hardware Drivers. See if the nvidia drivers there are installed properly. If so and it still doesn't work then you need to update your /etc/X11/xorg.conf file and specify that your device uses nvidia. You can do it manually or type "sudo nvidia-xconfig". Be sure to back up the xorg.conf file (though nvidia-xconfig should do it automatically) so you can revert back to your old .conf file if anything breaks.

2) It's connected? When you type "ifconfig" in a terminal, do you get an IP? I'm assuming that DHCP isn't working properly or something. Try typing the following:

sudo dhclient <adapter name, probably wlan0? Get this from ifconfig>
sudo ifconfig <adapter> down
sudo ifconfig <adapter> up

You could also just try clicking on the icon or something, since it should be refreshing (down/up) anyways... If it doesn't work, maybe contact your school's IT people? You never see the login page in ubuntu? Or it doesn't work AFTER the login page?

thanks for the help.but inever see the login page in ubuntu. i will try it and will reply soon.