Weird. My USB keyboard arrow keys + Pg down, page up - don't work within Mach 3 - but they DO work if I'm in another app like Notepad. Sometimes they don't work from the get go - today, they worked after initial boot, but after running a job, they didn't work. The Home key worked, and I can type letters and numbers into the MDI field. I re-checked if the keys worked in Notepad - they did.
It isn't the presence/absence of the onscreen pendant you bring up with the Tab key.
Quitting and restarting Mach3 brought them back just now - but hasn't always in the past.
Any ideas?