>Eventualy I've trapped the fail of locking tables, but sometimes the record still missing. At first the record is appendded succesfully because it could be viewed in the program and the other operation such as replacing the field is always succesfull.

It could be a bug,
but without a repro procedure,
VFPT cannot fix it.

On VFP9 exists a new option for FLUSH:

FLUSH [IN nWorkArea | cTableAlias] [FORCE]

Try the beta !?!

Fabio