Anti virus updates but cannot browse web page

Hello,

Our company uses a wireless router.

My business partner who uses Vista can connect to the internet with no problems. I however cannot and I'm using XP.
Very strange though, my laptop does all its updates and the antivirus does so aswel. When i try to browse the internet i cannot view the page - it always comes up with a DNS error. I have tried to use firefox too but to no avail. I can however go to my coffee shop round the corner and connect to their wireless network with no problems, just not at work. Please help me connect....