So I had X,Y and Z working in StepConfig... until I hooked up C41 and DB9. :(

Attach your hal and ini file, please.
You have most of the things right, is the DB9 for linit switches ?
You have spindle inputs wired, but i can see only 2 wires going to C41, should be 3 if you want to have reverse on the spindle also, leave that fo later.

I don't even have a HAL or INI file yet.

I'm still just trying to get through the configuration wizard to get this thing running right.

I've got X Y and Z working again, and they test fine.

I've got the C41 part way wired, but I found a schematic for the C41 to the KB120 controller baord (same basic board as mine) and the wiring I have now, which is basically a copy of what was in there with Mach, is defintiely incorrect. I think the original builder just used the mill once in awhile, and didn't have everything on teh C41 hooked up.

I talked to a guy on CNCZONE that just wired up a G0704 mill with a C41. He's got the parts out and on a table to bench test right now. I'm waiting for pics from him that show his wiring because he said he has spindle on/off and cw/ccw rotations available, so I'm gonna see if I can get those pics, replicate his wiring, and go on from there.

Will update as soon as I find something out. Thanks!