This problem is usually due to something going wrong in the startup code for your application.

Examine the walkback log, if one exists, for clues. This file could contain information about what errors occurred while executing the Smalltalk code.

Does Not Understand is a common error. Typically this occurs because the class which should have been instantiations before the message send which triggered the DNU was not included in the packaged image. The casses.es file can provide clues why.

To find out more about the problem, use the -l option on abt.exe (or nodialog.exe) to direct the default output to a log file. Invoke abt.exe again. Now examine the output log file.