DROP TABLE hangs because of same table foreign key

Hi,

On 7.2.1 debian-unstable PG hangs when trying to drop a table which
contains a field referencing another field in the same table as a
foreign key. 

Is it legal/orhtodox to use a "references" on another field of the same
table?
Strangely after restarting PG the drop succeeds without hanging.

--    OENONE: Vous aimez. On ne peut vaincre sa destinée.           Par un charme fatal vous fûtes entraînée.
                             (Phèdre, J-B Racine, acte 4, scène 6)