I believe I've solved my problem. In summary, the phenomenon of the UIRT not transmitting was caused by the sequence in which software was installed that calls the UIRT driver. This what I did.
I obtained a driver/device tester from the owner of the device—Jon Rees I believe. When I ran the software, which is very easy to do btw, capturing and transmitting worked flawlessly. I couldn't get it to fail. Therefore, it had to be something else interfering with the UIRT/driver.
I uninstalled Snapstream's software. I used Total Uninstall to make sure I cleaned out the registry and all traces (
www.martau.com). XP's Add/Remove Programs isn’t the best to use, imho. I left the UIRT/driver installed. I then re-installed SnapStream's BTV. I was able to remotely change channels through BTV. That is, the UIRT was transmitting. I then installed Snapstream's Firefly remote and I was still able to remotely change channels (with the Firefly device).
However, I found that installing the UIRT/driver AFTER installing Snapstream's Firefly remote, I wasn't able to remotely change channels. I think Snapstream ought to take another look at their routines. I'd suggest someone was careless in their coding/linking.