Many thanks Roberto, for the error identification I use this link:
https://docs.microsoft.com/en-us/windows/desktop/Debug/system-error-codes--0-499-
My problem looks something different, it is very sporadic, it happens that 2 dbf get the same file handle, maybe it is a problem of code, but looking in the code I was not able to found where this value is assigned...
It happens on my personal computer too, without no other user connect nor other program reading the dbf, if just after the error, i restart the program the program it does not happen again,
I don't know what i can do to remove this annoying problem.
Regards,