Version 11.0 Network Monitor does not capture any traffic and the following error is present in the PacketCapture.log:
06/21/10 02:15:26 [0x00001aec] INFO PacketCaptureMain - start() Packet Capture has started. System Event logged. [.\PacketCaptureMain.cpp(1750)]06/21/10 02:15:27 [0x00001f54] FATAL PacketCapture - Terminating capture thread -- Exception: PacketReceivePacket: 0 [.\CaptureThread.cpp(35)]
Ensure the required version 4.1.1 of WinPcap is installed.
See KB #54268 for related error and solution after an uninstall/reinstall was done.