It should not make a difference. I guess it something very high. If you realy need to know run:

SET ESCAPE ON
loc=CREATEOBJECT('combobox')
loc.RowSourceType=1
ln=1
DO WHILE .t.  
loc.AddItem(PADL(ln,11))
ln = ln+1
 IF ln/1000=INT(ln/1000) THEN
  ?ln
 ENDIF &&ln/1000=INT(ln/1000) 
ENDDO &&.t. 

and wait till it fails.

>thanks your reply, but i am facing when rows ource type=1