Railmonkey,
What revision of TIU do you have? Are you using a USB cable or a USB to Serial adapter?
A blinking TIU light on the WIU means the WIU can't connect to the TIU.
Something to also consider. The WIU can power the TIU via a USB connection but the WIU doesn't provide enough power to fully operate the TIU. You will want to make sure you have power to the FIXED 1 port or the AUX power port.