Y axis is making X axis stall...!!

[JAZZCNC]

Great news Steve. . I've known a few case's of failing or poor quality cables giving troubles, thou I still think it's your PP causing the problem. Thats why dropping the microstepping works.
Bet if you dropped the kernel speed to 25K you will be able to micro step higher.? . . . Give it a try and I think you'll find you can get 2000 M/S.!

Edit: The only reason to run higher Kernel speeds is if you can get higher speeds from your motor/screws than the kernel allows and your if PP is upto the job.
Other wise Mach works best or should say most stable at 25K. . . . If your happy to run at around 5mtr/min then I would leave it at 25K for best stabilty.