Selecting from a Subquery Fails

Hello, i have this big isuue:

i have 2 table referenced by this columns
codiceregistrazione=riferimentoesame;

select tipoesame,count(*) from righeaccettazione,registrazione where
codiceregistrazione=riferimentoesame and validita='VALIDO' and
dataesame between timestamp '2008-01-01 00:00:00' and '2008-12-31
23:58:59' and eseguitonellasegreteria=1 and ticket <> 2 and
repartoprovenienza=81 group by tipoesame order by tipoesame;

this query works fine (4 seconds to run as it is a large data set) and
produces 245 rows of values in 2 columns

if i try

select * from (

select tipoesame,count(*) as tot from righeaccettazione,registrazione
where codiceregistrazione=riferimentoesame and validita='VALIDO' and
dataesame between timestamp '2008-01-01 00:00:00' and '2008-12-31
23:58:59' and eseguitonellasegreteria=1 and ticket <> 2 and
repartoprovenienza=81 group by tipoesame order by tipoesame)

as ciao where ciao.tipoesame=615 ;

The query Hangs ....

can this be a bug or a misconfiguration?

thanks in advance