I've got a Windows XP machine running sp3 and I'm trying to connect to windows updates, but it's not connecting. I keep getting the following screen:

I can connect to the internet just fine, just not to windows updates. What's keeping me from connecting and what steps can I take to fix this?
Also, I checked and I can connect to norton.com and bitdefender.com, so I'm hesitant to think it's conficker.