>>>The PBxxxxAsync functions return almost immediately, i.e. before they
have completed their action. Your program is then supposed to wait
until they signal via a completion routine.

>>>If, as in your code, you do not wait for completion then you have a
race condition, leading to sporadic failures.

>>>Avoid all that by calling the correct routine PBHOpenSync. It returns
only after completing its job.

Thanks for your reply.  OK, I get that and will look for some documentation 
on the PBHOpen functions. What does FBwdToPBwd actually do, so I can 
understand why I am able to add it with, apparently, no effect except for 
changing the conditions affecting the critical race?

S