If it says you are "connected" but not getting the login screen you may have to get a new IP address. This can be done depending on your OS by right clicking the network connections icon at the lower right and choosing "repair". Otherwise go to start -> run -> type cmd then enter. Then type
ipconfig /release
then
ipconfig /renew

That helps me most of the time.

For Windows 7 its the same thing except type cmd in the search box to access the command line.