I have replaced my old computer with a newer machine running 32bit Windows 7.  The only software on the computer is Mach3. (run as Administrator)  It controls an Emco PC5 lathe with a vertical axis.  It ran flawlessly as a lathe or as a mill previously.  Now the hardware - running as a 3-axis mill - freezes after 1 to 2 hours running.  It will not jog until I have done a reset.  When I press TAB to get the 'flyout' continuous Jog works but step mode doesn't. Input on the MDI line has no response apart from a beep, no error messages appear.  If I press 'space' to pause and 'Esc' to stop the program whilst it is running all the above problems occur.  I have not tried the set-up as a lathe.
Any thoughts?