How does your new software send control characters to the machine? The numbers would most likely be associated with ASCII values and there are only probably a half dozen that get any usage. Check here: http://www.asciitable.com/
Perhaps try a simple program download to your PC and see if you can catch the correct characters that way. I suspect it is looking for a particular termination character, but the way that this is encoded into the DNC software could vary from program to program. For example, some programs use @003, others use ~003 to represent ASCII 003.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)