Can you put a breakmark before the USE and check your SET EXCLUSIVE setting? You could also try

USE mytable IN 0 SHARED

>My error routine is currently trapping errors and it says that the following line is causing the "File is in use by another user.":
> USE mytable IN 0
>
>I am trying to fix this but I can't reproduce the error "File is in use by another user.". I my testing I always get the "File Access Denied", assuming that the table is opened exclusively already.
>
>So far I have not been able to reproduce the "File is in use by another user." error.