That's strange. Unfortunately my mac-knowledge may not be sufficient to help you.
How new is your Mac, and which version were you installing?
(WireTap pro 1.3.2 Operating System Requirements:
This product is designed to run on the following operating systems:
Mac OS X 10.4 Intel
Mac OS X 10.4 PPC
Mac OS X 10.3.9
Mac OS X 10.3
Mac OS X 10.3 or later)
I have WireTap Studio 1.1.1,
Mac OS X 10.4 or later, QuickTime 7.0 or later, 1GHz G4 or faster, or any Intel Mac)
and it works well, you might try that one. (I have Mac OS X 10.5.