The best we can suggest is that you quit WireTap Pro, delete "com.ambrosiasw.wiretap_pro.plist" from your Macintosh HD/Users/Your_Username/Library/Preferences folder, and reinstall WireTap Pro. You can download the final version of WireTap Pro from:
WireTap Pro was discontinued in 2007 and is no longer sold or supported. It is not compatible with some 10.5.7 or later systems. It has been effectively replaced by [url=http://www.ambrosiasw.com/utilities/wiretap/]WireTap Studio[/url].