I posted this over on the Yahoo group but unfortunately I still can't get it to work
Here's my original post at Yahoo:

Hi
All of the sudden my index quit working. The true DRO would give a
reading and then go to 0 give a reading go to 0. I went to the
diagnostic page and the index LED will flash if you turn the spindle
by hand but as soon as you give it some RPM it stops reading and
flashes occasionally. I'm using the Omron reflective sensor and the
led on the sensor flashes in conjunction to the reflector. I have two
parallel ports and I tried different pin inputs on both ports. I put a
drill in the chuck and spun the spindle free of the VFD and got the
same results.
I have a CNC4PC breakout board on port 1 which was the original port.
And a Rutex motherboard on port 2.

This is really stumping me.

Thanks
Derek

Here's what I've tried since then
Replaced the sensor with a new spare
tried different spindle debounce settings
Tried a new cord to the Omron sensor.
Went from timing to index.

Again the spindle was working fine.
One thing that is constant is the red led on the omron sensor flashes in conjunction with the reflective strip and the led on the CNC4PC board flashes in conjunction with the sensor.
The index led on mach flashes when I turn the spindle slowly by hand but a soon as it gets some speed it stops reading accurately and starts flashing intermittently.

Thanks
Derek

This sounds like debounce is set way over the top. Everything is alright at slow speed - debounce doesn't really come into it. As soon as the sensor starts flashing faster, the debounce period is that long that Mach3 is only seeing the detector intermittantly - and in a completely pseudo random manner dependent on the speed of rotation.

As Jim said it could be debounce, could also be noise, do you have your wire shielded? Have you re-routed any wiring recently? Check all connections, especially the shield.
Do you have a scope? If so see what the pulse is like at the output of the sensor, move to the breakout then to other side of the breakout and finally the computer port. The last two wont be easy but if you have a smd grabber for the scope it will be no problem, if you dont then you will have to improvise.
 If you dont have a scope then possibly use a voltmeter on the mV range, not nearly so effective but should at least let you compare the signal as it proceeds through the hardware, if there is a big difference then you should be able to pinpoint where the problem is.

Hood

Thanks for the help guys.
I agree with both suggestions as being debounce or noise. Is it possible that Mach is not accepting the changes in the index debounce field? Like it's stuck or something.
The cable isn't shielded and at this stage it's completely outside the cabinet.
I have a scope but I'm embarrassed to say I'm not exactly comfortable using it. Ive tried to use it a few times but have never been confident that the settings on the scope were correct and my grounding techniques were proper so I didn't trust the data. I guess it's time for me to go to oscope school !!  I'll order in a couple of those grabbers as well. They look to be fairly handy. I know that the fact that it worked before has nothing to do with noise issues. I've been down that road many times.

Thanks
Derek

Dont be embarrassed about anything, its better to be wary of things you are not sure of than be over confident and make things worse. I have attached a scope basics document, it might be of use to you.
Hood

Oh meant to say you could try setting up another profile to see if the index works in it, no need to set up motors etc, just the Index and anything else you need for the spindle control.

Hood

Increase the size of your color strip, at higher speeds, the "On" time duration will need to be long enough for mach to see it. Further if you debounce is set to high, you led may turn off prior to your debounce settting turining off.

Scott

This might sound like a daft suggestion but at this point I guess you don't mind them!

Does the diagnostic light come on the right way around? i.e. only when the slot lines up with the sensor? If the light comes on when the sensor can't see through the slot then you may have toggled the "active low" setting by mistake.

yeap flip the active high/low

Thanks for all the suggestions

I unchecked the active high just for fun and the only thing that did was convince my CNC4PC board to finally take a dump. This thing has given me nothing but problems since the day I bought it. I'm moving on to something else. Probably a Campbell combo.
Here's what I tried and if this is crap feel free to let me know. I unhooked the parallel cable from the CNC4Pc board. I connected a wire to pin 15 my current pin choice. If I touch the wire to the ground the LED index light goes on or off depending how I have Mach set. If I tap the wire against the ground at a slow rate the led flickers fine. As soon as I pick up the pace the led either stays lit or doesn't light depending on whether it's active high or low. I tried index debounce settings from 0 to 1000 and it didn't change a bit.

Derek