Cannot connect to wireless connection at home but can elsewhere...

So, my roommate has a Dell, Vista platform and I have a Mac. I will bullet point the details to make this as clear and concise as possible:
1. Spent the past 6 months "borrowing" a wireless connection from neighbors with no problems.
2. Moved to a new location and the Mac can connect to available wireless signal but though PC says it is connected, it will not open a page.
3. Was able to connect to wireless networks anywhere outside of apartment.
4. Scheduled installation of Comcast Ethernet modem connection.
5. Tech was unable to open web page even when ethernet cable was directly connected to PC
6. Still able to connect to wireless networks outside of apartment.
7. Still states there is a connection, but after much time trying to open a page, it is ultimately unable to connect to wireless connection in apartment.

HELP- OUR SANITY IS ON THE LINE HERE! Graduate student NEEDS internet connection at home.
Thank you for ANY help you can provide! =)

Hello,

So the problem here is that the Vista computer is unable to connect? The person you are "borrowing" the connection from might be blocking your access probably through MAC address filtering.

Well the biggest confusion is stemming from the fact that when the tech came to actually install a physical ethernet connection in our apartment, she was still unable to connect. He connected the cable directly to her computer and though it said she was connected, could not open a page.
As mentioned, she can connect on other wireless networks, so maybe the tech situation was just a coincidence?
We tried the Winsock download and that has not resolved the problem.