That sounds super strange. From what I understand, Racket automatically caches modules, so they are only loaded once.
But then again, Racket does have multiple phases, so it's possible that it's loading the "compiler" file in two different phases, causing duplicate variable definitions.
In addition, Racket doesn't allow for mutually recursive modules, but Arc/Nu is using "namespace-require", which apparently bypasses that restriction. It's possible that there is a race condition that is causing the "arc/3.1/main" file to be loaded before the "compiler" file is finished loading, which then triggers a second load of the "compiler" file.
Just to clarify: have you tried inserting a "displayln" in the "compiler" file to verify that it is being loaded twice?
