Differential encoder hard crashes the PC MESA7i77

ok guys, overwhelming responses!! Thank you all for the awesome support!!

I do have a spindle, z, and x encoder, all attached to servo drives. I do not have the drives powered right now because I do not want to attach anything else for fear that I've done something wrong in the config/pin out. I can afford to replace an MPG, I cannot afford to replace a drive...

The original MPGs that came with the machine (Fryer ET18) are labeled as OLM-01-2AD by Maxmar Controls Inc. I presumed (as unlikley as it was) that both MPGs were bad because they both (X and Z) would crash the computer if they moved even one pulse.
The replacement MPGs are no-name Chinese, but are also 6 wire, 5VDC differential encoders. Pictures of those are in my previous posts. It doesnt appear to matter though, the new encoders make the machine behave the same as the old encoders. I am unable to find an official spec sheet for these, but the google claims they are standard quadrature A/B rotary MPG 5VD.

guys, the 7i77 is fed off an independent 5vdc power supply, switches are set appropriately.