First of all overwrite all common files with the new ones. For example with unix shell cp -r obliquid-0.9.1/common/ obliquid-0.9.0/, or you can overwrite the common dir using ftp

Execute the following queries -- If your prefix is not sl_, adjust accordingly

CREATE TABLE _sequence_sl_tabledesc (
  sequence int(11) NOT NULL auto_increment,
  PRIMARY KEY  (sequence)
) TYPE=MyISAM AUTO_INCREMENT=100001;

INSERT INTO _sequence_sl_tabledesc VALUES (100000);

ALTER TABLE sl_doc_cat1 ADD id_parent INT NOT NULL;

CREATE TABLE _sequence_sl_doc_cat1_parent (
  sequence int(11) NOT NULL auto_increment,
  PRIMARY KEY  (sequence)
) TYPE=MyISAM AUTO_INCREMENT=1;

CREATE TABLE sl_doc_cat1_parent (
  id_doc_cat1_parent int(11) NOT NULL default '0',
  name char(80) NOT NULL default '',
  UNIQUE KEY doc_cat1 (id_doc_cat1_parent)
) TYPE=MyISAM;

INSERT INTO sl_tabledesc (id_tabledesc, tablename, field, type, length, is_primary) VALUES (2705, 'doc_cat1', 'id_parent', 'integer', 0, 'N');
INSERT INTO sl_tabledesc (id_tabledesc, tablename, field, type, length, is_primary) VALUES (2706, 'doc_cat1_parent', 'id_doc_cat1_parent', 'integer', 0, 'Y');
INSERT INTO sl_tabledesc (id_tabledesc, tablename, field, type, length, is_primary) VALUES (2707, 'doc_cat1_parent', 'name', 'text', 80, 'N');

INSERT INTO sl_configparms (name, setting, description, id_module, ord) VALUES ('cat1_parent', 'N', 'Use category 1 with parent (doublecombo)', 5, 50);
INSERT INTO sl_configparms (name, setting, description, id_module, ord) VALUES ('signup_enable', 'Y', 'Allow guests to create a new user record.', 2, 15);

UPDATE sl_slotfield SET label = '#passwd' WHERE `d_slotfield = 422;

The new roles cal_view and cal_adm have been introduced. security_partial, security_full, doc_adm and site_conf have been modified.