Hard Mode error message

Question

I have a number of checkboxes on the screen and all of a sudden I am getting
an error message - Hard Mode. What does this mean?

Answer

A:
16Q) What does the debugger message "Debugger Is Unable To Stop
    Due To 'Hard Mode' " mean?
16A) DEFINITION:Hard mode is a state of Windows when no message
    processing can take place. It happens during menu drawing
    and some kernel operations.  It means that you are in a
    state that Delphi can not "freeze" your application without
    locking up Windows. Typically, that arises as a result of 
    multiple SendMessage calls. In addition a workaround which 
    often works: What you need to do is kick the system out of 
    hard mode. Interestingly enough, this can happen when the
    debugger puts up the system modal messagebox to tell you it's 
    in hard mode! So try putting an additional breakpoint on the
    line *before* your breakpoint. This first one will cause the 
    hard mode warning and should kick Windows out of hard mode. 
    When you OK that messagebox the second, desired, breakpoint
    should work.
       NOTE: Since the debugger is message driven, it cannot 
             allow you to stop at a breakpoint if it thinks 
             the system is in hard mode, because you wouldn't
             be able to do anything and the system would appear
             to be hung.

[Borland Delphi FAQ]