Ip address

Hi, i always ahve this exclamation mark in a yellow triangle on the bottom right of my desktop, and when i click it, it says limited or no activity, and it has the same name as my modem, globespan usb adsl modem,

but im on the internet now, so why would it say limited or no activity

anyway, when i click on it, it gives me the option of repairing it, and i do, and it says renewing ip address, but then it says it was unable to repair it, and to contact your network manager or somthing, and triangle is still and always there