That's strange, sounds like they are either blocking the IP or, you have some software running on your machine or some configuration setting that is blocking access.
What happens when you try to contact powerusenet from the windows command prompt?
Try the following and see what results you get:
ping
www.powerusenet.com
ping news.powerusenet.com
telnet news.powerusenet.com 119
If the first 2 fail, look at the IP that is returned when you do the ping command. For me, it is 217.160.249.92 for www and 216.196.97.161 for news. If the first 2 tests pass but the telnet fails, then try again using alternate ports of 23 and 80 and see if you can get a connection.