John,
You mentioned earlier that sometimes you were getting motion and sometimes you were not. Almost sounds like an intermittent connection somewhere, maybe something to do with the enable line?
Another place to check (I got bit by this once) signal commons.
I converted an old machine once for the local high school that bought this machine 10 years earlier, used it for 1 week, and it died and the mfg was no longer in business. I didn't use a breakout board just wired the parallel port directly to drivers and switches using pullups and current limiters, but forgot to bring the parallel port ground over to the 5v signal common. It would run fine sometimes depending on what outlets it was plugged into, then other times only half the machine would work.
Arnie