Basically, Access 2003 terminates viciously - The entire application disappears completely. Nothing is even left in the Task Manager.
I have read that the SetWindowsHookEx library call installs a hook procedure that intercepts messages before they get to the destination window.
When I run the code in a more limited environment, everything works fine and my target window gets modified as expected. However, when I drag the same code into my more complex environment with tons o' tabs, buttons, and subforms, Access dies a sudden (though hopefully painless) death.
The problem was with the "Declare Function SendMessage" declaration(s) that I had in my code.
The code I imported that was using the SetWindowsHookEx function had a different (and the correct) prototype for SendMessage. My old code had a different (and incorrect) prototype for SendMessage that wasn't being used previously.
Not knowing this, I had used the older incorrect prototype, and had commented out the newer correct prototype.
Once I saw the difference, and enabled the newer SendMessage prototype, everything is working fine.