JP1 Remotes

Newbie here - and in spite of the extensive posts and help to be found, I'm stumped.
I have RCA RCRP05B (black) remote but that doesn't seem to be an issue - yet.
I had built a JP1 EEPROM interface, which was the wrong one, as I found out through the forums. So I built a 'discrete transistor version of JP1.2/3 interface' from the plans in the file section. Now, when I start IR (any version up to and including 8.03) and set the connection to 'JP1.x Serial or USB', I always get the 'failed to open interface', remote connected to interface or not.
I have tried a serial port sniffer, and while it reports that IR has opened the port - and closes it - no data is ever sent. Version 8.03 opens and closes it when you try the interface, while the older ones opens and closed the port when the program started and exited - but I digress.
If I tie serial port connections 2 and 3 together (at the interface board) to create a loopback interface, hyperterminal indicates that the com port is working just fine. Starting IR with the 'loopback' in place has the same error message, however.
How can I determine if I made a mistake in the interface (which I have checked many times, but you never really know until it works) or have another problem with the cable/com port/computer/software compatibility?
Does the remote need to be connected to test for an interface with this type of interface? What is IR looking for to determine the interface is there?
Is there some table of DTR, Tx, RTS and Rx states that I could check? Generally, with IR running I am seeing them all steady state at -10Vdc except Rx, which is -0.6Vdc (DVM measured from pin 5). No apparent changes on IR start or interface check.

There's a great document by Tommy Tyler in the file section here:
How to test and troubleshoot a Serial Interface for JP1.2 and JP1.3
That document walks you through various tests for your interface, using jp1xtest.exe (also available in the file section), and some other techniques.

One of the things that document says is:

The worst way to test a JP1.2/3 interface is by trying to use IR.exe. ... The best way to test a JP1.2/3 interface is with a test program (jp1xtest.exe) that was developed specifically for that purpose.

Well, I don't know what to say. I did a PC shutdown, unplugged the power for a few minutes - and - voila! Everything works!
Great troubleshooting guide though. I went through what it said, and it all checked out.
One tiny note - where the guide talks about the COMTEST program 'always opens with DTR on and RTS off. Each time you click on a button it toggles that signal on and off' - well, the version of the program I downloaded has me use the hot-key 'Ctrl-D' and 'Ctrl-R' to toggle the state of DTR and RTS. I though there was something wrong when clicking on the red 'button' on the screen did not toggle the state of DTR.

Thanks a million to the many that brought me this far!!

Now, on to the real meat of the issue - getting the remote to 'dance' for me.

driver wrote:I did a PC shutdown, unplugged the power for a few minutes - and - voila! Everything works!

Good news!
I love problems that just solve themselves...