Login onto 2000 Server problem

I have windows XP on my laptop and i connect to a windows 2000 Server at work. I was able to access the computers on the domain for a couple of months but now all of a sudden i can’t access them. I am still able to access the internet and i can ping around the network but i can’t access the computers through My Network Places. The only thing that i have changed to my knowledge is i went from a wireless card to a ethernet cable plugged into the hub. I don’t think i changed anything else. If someone could offer me some advice that would be great. Thanks.