I had an issue where I THOUGHT everything was wired correctly, but when I did Ultimarc's Keyboard pass-thru test, it showed that I had 2 shorted switches. I followed the instructions below, figured out which shorted keys I had. Once I corrected those shorted switches, the programming worked correctly. I couldn't see the shorted switches until I connnected up the keyboard pass-thru and set the iPac to the test mode (as outlined below)
From ultimarc;
Problem: No shift functions work.
Part of the shift function design means that to avoid "stuck" keys, shift functions are disabled when any key is pressed. So loss of shift functions means you have a shorted or stuck switch. Problem is, which one? There are two ways to determine this. The on-board LED gives an indication of which input is shorted, see later in this section.
Or use the built-in test mode:
Run any text-display program such as Notepad, or if you are in DOS type "COPY CON" to turn off the command prompt. With a keyboard plugged into the pass-through port, press CTRL-ALT-P (press and hold each key in this order). You will go into programming mode. If the MAME/ALT jumper is set to MAME you will go right into test mode. If not, you will see a menu. Enter "T" for test mode. The offending stuck input(s) will be displayed on the screen.
Problem: Cannot program. Utility hangs at end of programming.
One cause of this is having non-switch items connected to inputs. In general, the inputs must be "open" (ie no switch pressed) for programming to work. This may not be the case if you have other things connected such as a game board connected at the same time as the I-PAC. Email for further advice on this if you must have other devices connected as there are workarounds.