EagleFiler uses AppleScripts to capture from applications, including NetNewsWire. When EagleFiler sees that NetNewsWire is running, it tries to compile the script that it will use to communicate with NetNewsWire. Unfortunately, NetNewsWire Lite declares itself using the same application identifier as the full NetNewsWire, even though Lite is not scriptable. So EagleFiler thinks the full NetNewsWire is running and asks the OS to compile the script. The OS can’t find NetNewsWire, so it asks you to locate it. Sometimes, AppleScript will even crash when trying to load the script if it can’t find the full NetNewsWire.
An upcoming version of EagleFiler will work around these problems. For now, one workaround is to not run NetNewsWire Lite at the same time as EagleFiler. Another is to delete the file: EagleFiler.app/Contents/Resources/Capture Scripts/com.ranchero.NetNewsWire.applescript if you are using Lite.