Take a look at Cannot access selected table error FAQ #18812.

>There's a form with a combo. I use the code below in the combos' gotfocus event. When the form running and the combo loses and after gets its focus back, I get the error message: "Cannot access the selected table". Why cant I have access to the tables when they are open?
>
>
>lnCntUsed = AUSED( laUsed )
>FOR lnSessCnt = 1 TO lnCntUsed
>SELECT ( laUsed[lnSessCnt,2] )
>IF CURSORGETPROP( 'Buffering' ) > 1
>TABLEREVERT( .T. )
>ENDIF
>USE
>NEXT
>
>USE table1 IN 1
>USE table2 IN 2