There is not a specific code which causes this error
anyway it occurs in the moveclick()code after I process this code:

Do form 'officina' with Iif(Empty(lcScheda),1,0),lcscheda,&lcDatac,&lcContatto

Select 'wanagraf'
Locate for codcli = lcCodcli
If !Found()
	Locate
EndIf 	
If Type("Officina") = 'O' and IsNull(officina)
	Release officina
EndIf 	
thisform.pulsanti.moveclick(0)
Return 

here is the Moveclick procedure :

parameters nrc
NoDefault 
If thisform.edit = 0
	Set Near off
************************** HERE IS where I GOT THE ERROR
	If !Used('clienti')
		Use clienti Again In 0
	EndIf 
	If Empty(Sys(14,1,'clienti'))
		Select 'clienti'
		Set Index To 'clienti1'
	EndIf 	
	=Seek(wanagraf.CODCLI,'clienti',1)
	Set Near On
EndIf 	
With thisform.pgf.pg1.grd
	.recordsource = ''
	If thisform.tipo = 'C'
		Select contatti.idc,datac,orac,contatti.referente,Left(notecnt,120) as 'note', ;
			idage,giorno,orario,Left(noteage,120) as 'noteage' ;
			from 'contatti' left join 'agenda' ;
			on contatti.idc == agenda.idc ;
			where contatti.codcli == clienti.codcli ;
		union ;
			Select idc,Ctod('') as 'datac', Space(5) as 'orac',Space(60) as 'referente', ;
				Space(120) as 'notecnt',idage,giorno,orario, ;
				Left(noteage,120) as 'noteage' ;
		 	from 'agenda' ; 
			where agenda.codcli == clienti.codcli and Empty(idc);
			into cursor 'wconta' ;
			order by 2,3,7,8  ;

			
			.recordsource = 'wconta'
			.column1.controlsource = "dtoc(wconta.datac) + ' ' + wconta.orac"
			.column2.controlsource = "wconta.referente"
			.column3.controlsource = "dtoc(wconta.giorno) + ' ' + wconta.orario"
			.column2.header1.caption = "Referente"
			.column1.header1.caption = "Contatto"
			.column3.header1.caption = "Appuntamento"

	Else
		Select idage,giorno,orario,Left(noteage,120) as 'noteage' ;
		 	from 'agenda' ; 
			where agenda.codrap == tabrap.codrap ;
			into cursor 'wconta' ;
			order by 2,3 
			.recordsource = 'wconta'
			.column1.controlsource = "dtoc(wconta.giorno) + ' ' + wconta.orario"
			.column2.controlsource = "wconta.noteage"
			.column2.width = 230	
			.column3.width = 1
			.column2.header1.caption = "Annotazioni"
			.column1.header1.caption = "Appuntamento"
	EndIf 		
EndWith 
thisform.Refresh()
thisform.pgf.pg1.grd.SetFocus()

If Eof(thisform.pgf.pg1.grd.recordsource)
	=Seek(Replicate(Chr(154),10),'contatti','idc')
endif	

With thisform.pgf.pg1.cntConta 
	If Type(".scheda") = 'O' and !IsNull(.scheda)
		.removeobject('scheda')
	EndIf 	
	If Seek(contatti.idc,'schede','idc')
		=Seek(schede.id,'schedet','id')
	EndIf 	
	
	.refresh()
EndWith 			
thisform.loadscheda()
thisform.LockScreen= .f.