>Thanks for your reply. It gave me a thought: in your situation, have you ever tried replacing APPEND BLANK with INSERT INTO (SQl); if so, any help?

I have a 145 MB table of items and 30 MB table of order and invoice rows.
Users create invoices from orders. VFP 5 build 415, NT4 SP6 server.

Server: 2x Accton 1207B-TX 100/10 (DECchip 21140). Server motherboard
ASUS P2L97-DS (2x 233 MHz PII, 128 MB RAD, soft RAID 1 (mirror))

Switch: 2x 3Com Superstack 1100, 2x 100, 24x 10.

This occurs both in NT and Win 98 workstations and both in 10 MB and 100 MB
segments.

I replaced append with insert into command but this doesnt help.
Some times a day, a duplicate invoice headers will randomly
appended to file.

I tried to switch opportunistic file locking off
(http://support.microsoft.com/support/kb/articles/Q129/2/02.asp,

http://msdn.microsoft.com/library/psdk/winbase/fsys_9s4z.htm).

but this doesnt help.

Can anybody help me ?