Windows 7, "Network Shield" when using "Internet Explorer can not display the webpage" is displayed.
Windows 7 or Sp1 are both displayed the same results.
avast! "Network Shield" OFF -> Internet Explorer, the normal output.
All the same, changing the hardware drivers and software.
If you try 10 times, more than 3 times are displayed.
Test Environment
Windows 7 64bit + Sp1 (vista and xp than if you did not)
avast! IS Ver. 5.1.889 (free version of the same results)
Internet Explorer 8 (32bit and 64bit the same results)