This message can sometimes appear after updating to Windows 8.1. Most likely, the update has deleted some necessary files. Uninstall WinPcap using the WIndows Control Panel. Reboot. Reinstall WinPcap 4.1.3 or greater. It is distributed inside the Replay Media Catcher 5 directory in C:\Program Files (x86)\Applian Technologies\, or it can be obtained from www.winpcap.org. During installation, make sure to leave the "launch at startup" button checked. Then run Replay Media Catcher 5 and check Settings->Internet->Monitor to make sure Use WinPcap is selected.