So as I said, I'd come back on where the resource file is used.
In fact it's in setting and restoring the environment.
I suspect this to be a bug in case you don't have a resource file (SET RESOURCE = OFF) or it can't be found. SET RESOURCE was on in the dev environment but no foxuser in the runtime environment.
If you check out the code in classlib common30\libs\CEnviron.vcx in CGlobalEnvironment::Set()and CGlobalEnvironment::Reset().
Just be comparing the Reset() code with the Set() code I saw a comment for the SET RESOURCE TO in the Reset() where they already encountered a particulary problem.
And they have some extra code for bulletproofing the code.
This is not in the Set() method, maybe here lies the problem.

Ahum, I was a bit lazy to run the code. That's why I'm just assuming and pseudo bug/problem fixing.