Please go to the menu of Parallels Desktop "Preferences" -> Networking and click "Restore Defaults".
Then shutdown the VM. Make sure that it is in the "Shared Networking" mode. Boot the VM again.
If this doesn't help, click Start -> Run and execute cmd.exe. Type in the appeared window command "ipconfig /all". Then, without closing the window, click Parallels Destkop menu "Help"->"Report a Problem", send a problem report (it is not necessary to provide description) and post here the report ID.