Problems with temp table and PL

I create a temp table inside a plpgsql function, which is drop just before
ending (the function).

My problem is that if I execute the same function again (in the same
session) I get an error when trying to insert data into it (looks like the
session has an old reference of the table):

=> SELECT actualizacionAnualProximoHabil(2008);
ERROR:  relation with OID 9668312 does not exist
CONTEXT:  SQL statement "INSERT INTO dias_semana VALUES ( $1 )"
PL/pgSQL function "actualizacionanualproximohabil" line 9 at SQL statement

As I said, the first execution works OK, but from then on it gives this
error, until I close the session and open it again.

Any ideas?

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