You have listed the various keyboard  types but haven't said whether there is
any pattern between keyboard type and successful break.

Try using Escape to do the break. It might work more reliably.

there really isn't a successful patter between keyboard  type and success...
only one computer  (mine but i'm not really one who's to use this.. i'm just
trying to trouble shoot it is the only one that is successful with all the
keyboard types)... some work with the usb  others with the ps-2..... i'll
suggest/try the escape key to see if that works....

I don't have an answer for the CTRL + Break situation, but I am
wondering why this is a concern at all?! Why are you relying on this
method to stop a program? From my point of view it is incorrect, and
clearly unreliable.

well the Escape key seems to work... as for why we are needing this... it's a
temp fix for an occasional endless loop that occurs due to certain information
input incorrectly (not on our end but on some db query info that we connect to)
that we haven't been able (so far) to handle error  wise....