Problems in queries

Hi all
I have this function:
 def checkNameDob(self, name, dob):
        cur = self.conn.cursor();
     
        sql = "SELECT * from patient WHERE fn_pat = %s"
        cur.execute(sql,(name))
        rows = cur.fetchall()

It seems to work fine, But I'm getting this exception:
psycopg2.ProgrammingError: current transaction is aborted, commands ignored until end of transaction block
at: cur.execute(sql)

What's the problem?
thx

ps: fn_pat is the column of the db, name is the string passed in the function parameter.
if I type:
"SELECT * from patient WHERE fn_pat = 'david' "
in the psql on console it works well...