>>To be clear : Can you confirm that it is the CopyFile() that is throwing the exception - not the second program that attempts to access the file.....
>
>...it is the copy file.
>
>>Should be in the exception stack ?
>
>Yes, but this is a very rare situation and I cannot reproduce it right now.

Probably stuck on discovering the source of the problem without it :-{

Does the .tmp file renaming approach work ? If the second program attempts to copy that whilst it's still .tmp then you're back where you started......