This is a new one.  I've been using Mach3 for over six years and never had anything close to this happen.  Was running a job (2+ hours into g-code) on CNC router when the "B" motor (slaved to Y) suddenly locked.  After much trouble shooting determined it only occurs when I attempt to jog in step mode.  Jogs normal in continuous mode.  This occurs when using either Shuttle Pro or Tab flyout.  Disabled and removed Shuttle Pro without change.  Any ideas on how to fix?

Does it do the same if you use the keyboard? or is that what you are meaning by using the flyout?
Hood

Have not tried the keyboard, just the flyout when you hit tab to show display.  Have also tried to run a program with jog off; same result, B (slave) would not move.

Cant think what could cause that I am afraid.
If you want to attach your xml I can have a look through it to see if I can find a problem.
Hood

Finally got it working this morning.  This was after troubleshooting about every combination of things could think of, including uninstalling all software and plugs, reinstalling and building XML over.  B slaved to Y still did not work.  Then slaved A to Y and worked.  Still don't know why slaving B to Y does not work as I have been using that config. for the past year. 

Cant think what could cause that I am afraid.
If you want to attach your xml I can have a look through it to see if I can find a problem.
Hood