Hi Ed,
You're not the only one to have issues like this for sure. It takes a little investigating to narrow down the cause, but you'll get there.
Here's a good USB/Serial adapter. The adapter allows you to connect from the WIU's USB port to the 9-pin serial port on the TIU. This is how you have to connect Rev. G through Rev. I TIU's that don't have a USB port, and it's a good option for connecting Rev. L TIU's on layouts with heavy app traffic. There are many USB/Serial adapters available. The key features of the unit I linked to above are the Prolific PL2303 chipset and thumb screws so you can connect directly to the TIU's 9-pin serial port.
