There's a million ways to crash a machine - get round this one and they'll find another!
Seems to me either your operator was having an off-day, (even the best guys have a hangover occasionally) or you need to look at your operator training. He's just had the best training already though - make a 4grand error and it's unlikely he'll forget to check his offsets again...
You could write a macro to check that the tool offset a tool is looking at isn't something silly, but if there's a big difference between your shortest and longest tools, then you'd have to write a seperate one for each tool - meaning you're effectivly checking the offsets manually anyway.
Some machines have 'soft limits' you can set around things like chucks and fixtures, creating 'no go' areas for the tool regardless of programming moves or offset values. In other words, if you move into the envelope you describe the machine will error out, no matter what. Might be worth checking if you machine will do that?
Excessive accuaracy is a sign of poor breeding. -Socrates.