Throw away ".zo" versions of your source.
Prefix your program with
or start MzScheme with the -l option before the arguments to load your program:
mzscheme -l errortrace ...
If you want to use MzScheme interactively, include the -i flag first:
mzscheme -i -l errortrace
When an exception occurs, the exception handler prints something like a stack trace, most recent contexts first.
The errortrace module is strange; don’t import it into another module. Instead, the errortrace module is meant to be invoked from the top-level, so that it can install an evaluation handler, exception handler, etc.