Right after you get .F. for the TABLEUPDATE(), do the following from the Command Window:

AERROR(laError)
DISP MEMO LIKE laError

Then reply with the error information.

>TableUpdate returns .F. if I modify an existing record and .t. if I insert a new record.
>
>>What TABLEUPDATE() returns? .t. or .f.. If it returns .f. You can use AERRORS() to check what cause the problems