Mark,

Firs you don';t need a transaction for one tableupdate().
Second you are ignoring the return vlaue form the tableupdate() which is probably returning .F. because it failed.

Try code like this;

SELECT vPieces
IF ThisForm.AddMode
   REPLACE keylink WITH ThisForm.CurrKeyLink
   REPLACE created WITH DATETIME()
   REPLACE createdby WITH oApp.CurrentUser
ENDIF
IF TABLEUPDATE(.F.,.F.,"vPieces") && use .f. as the first argument because you
                                  && only have one record to update
   REQUERY('vPieces')
ELSE
   Wait Window "Update Failed"
   TableRevert(.T.)
ENDIF