Uninstall any third party firewalls (Comodo, ZoneAlarm, etc) temporarily turn off the Windows 7 built in firewall for debugging. Uninstall any third party Antivirus / Internet Security Suites that may have some type of firewall applet as part of their software. You can always reinstall them later if they prove not to be at issue.
Also right click a blank area of the taskbar and choose "Start Task Manager"
at the top of the task manager console select the processes tab
look for something called mdnsresponder.exe
if it is present post back and we'll address that issue.
EDIT: Forgot to mention in task manager, make sure you check the box near the bottom left that says "Show processes from all users"