> anything else i need to look at?

So you have any global key hooks in place such as ON KEY LABEL, BindEvent, etc.? They would interfere with the debugger. Same if you use timers in your application (unlikely with your DOS app, but still...)

How are you opening the debugger? DEBUG will open the debugger put but not put it into debug mode. SET STEP ON and ASSERT .F. both turn the debugger into debug mode.