Sam,
Now that you know the correct way to do it, I am not sure if it is worth to waste time on this, but, it works fine for me unless there is actually no table opened in the current work area, otherwise it does not give an error, even when it does not work (EOF on either or both table, for example).
[Update]
Oh, and by the way, the error is logical, because if you use REPLACE without the IN clause, it assumes IN the current work area, which is empty
"The five senses obstruct or deform the apprehension of reality."
Jorge L. Borges?
"Premature optimization is the root of all evil in programming."
Donald Knuth, repeating C. A. R. Hoare
"To die for a religion is easier than to live it absolutely"
Jorge L. Borges
