Neil,
As Tore said are you sure DO generatepdffab is fired? VFP waits until procedure is finished and then continues on the next line of code, so put some WAIT WINDOWs in CASEs to see if the right CASE is being used:
I see you do exactly the same in these 2 cases, so you can modify the like this:

IF (m.fabstatus == 'Pending Approval' OR m.fabstatus='Approved') AND thisform.fabstatus.Value='Approved'
   SELECT fabsum
   TABLEUPDATE(.T.)
   thisform.resetmode
   WAIT WINDOW "Before generatepdffab" NOWAIT NOCLEAR
   DO generatepdffab
   WAIT WINDOW "AFTER generatepdffab" NOWAIT NOCLEAR
ELSE
  WAIT WINDOW "generatepdffab IS NOT FIRED"
ENDIF
WAIT WINDOW "BEFORE locatearticle" NOWAIT NOCLEAR
DO locatearticle WITH cArtikey
WAIT WINDOW "AFTER locatearticle"
WAIT CLEAR

RETURN