I have the same issue.

2013-01-30 12:22:43,775 6483 ERROR demo001 openerp.sql_db: bad query: delete from wizard_multi_charts_accounts where id IN (1)
Traceback (most recent call last):
  File "/opt/openerp/server/openerp/sql_db.py", line 227, in execute
    res = self._obj.execute(query, params)
IntegrityError: null value in column "bank_account_id" violates not-null constraint
CONTEXT:  SQL statement "UPDATE ONLY "public"."account_bank_accounts_wizard" SET "bank_account_id" = NULL WHERE $1 OPERATOR(pg_catalog.=) "bank_account_id""

2013-01-30 12:22:43,778 6483 ERROR demo001 openerp.addons.base.ir.ir_cron: Call of self.pool.get('osv_memory.autovacuum').power_on(cr, uid, *()) failed in Job 1
Traceback (most recent call last):
  File "/opt/openerp/server/openerp/addons/base/ir/ir_cron.py", line 132, in _callback
    method(cr, uid, *args)
  File "/opt/openerp/server/openerp/addons/base/ir/osv_memory_autovacuum.py", line 31, in power_on
    model._transient_vacuum(cr, uid, force=True)
  File "/opt/openerp/server/openerp/osv/orm.py", line 5191, in _transient_vacuum
    self._transient_clean_rows_older_than(cr, self._transient_max_hours * 60 * 60)
  File "/opt/openerp/server/openerp/osv/orm.py", line 5155, in _transient_clean_rows_older_than
    self.unlink(cr, SUPERUSER_ID, ids)
  File "/opt/openerp/server/openerp/osv/orm.py", line 3976, in unlink
    'where id IN %s', (sub_ids,))
  File "/opt/openerp/server/openerp/sql_db.py", line 162, in wrapper
    return f(self, *args, **kwargs)
  File "/opt/openerp/server/openerp/sql_db.py", line 227, in execute
    res = self._obj.execute(query, params)
IntegrityError: null value in column "bank_account_id" violates not-null constraint
CONTEXT:  SQL statement "UPDATE ONLY "public"."account_bank_accounts_wizard" SET "bank_account_id" = NULL WHERE $1 OPERATOR(pg_catalog.=) "bank_account_id""

2013-01-30 12:53:15,291 6483 ERROR demo001 openerp.sql_db: bad query: delete from wizard_multi_charts_accounts where id IN (1)
Traceback (most recent call last):
  File "/opt/openerp/server/openerp/sql_db.py", line 227, in execute
    res = self._obj.execute(query, params)
IntegrityError: null value in column "bank_account_id" violates not-null constraint
CONTEXT:  SQL statement "UPDATE ONLY "public"."account_bank_accounts_wizard" SET "bank_account_id" = NULL WHERE $1 OPERATOR(pg_catalog.=) "bank_account_id""

2013-01-30 12:53:15,294 6483 ERROR demo001 openerp.addons.base.ir.ir_cron: Call of self.pool.get('osv_memory.autovacuum').power_on(cr, uid, *()) failed in Job 1
Traceback (most recent call last):
  File "/opt/openerp/server/openerp/addons/base/ir/ir_cron.py", line 132, in _callback
    method(cr, uid, *args)
  File "/opt/openerp/server/openerp/addons/base/ir/osv_memory_autovacuum.py", line 31, in power_on
    model._transient_vacuum(cr, uid, force=True)
  File "/opt/openerp/server/openerp/osv/orm.py", line 5191, in _transient_vacuum
    self._transient_clean_rows_older_than(cr, self._transient_max_hours * 60 * 60)
  File "/opt/openerp/server/openerp/osv/orm.py", line 5155, in _transient_clean_rows_older_than
    self.unlink(cr, SUPERUSER_ID, ids)
  File "/opt/openerp/server/openerp/osv/orm.py", line 3976, in unlink
    'where id IN %s', (sub_ids,))
  File "/opt/openerp/server/openerp/sql_db.py", line 162, in wrapper
    return f(self, *args, **kwargs)
  File "/opt/openerp/server/openerp/sql_db.py", line 227, in execute
    res = self._obj.execute(query, params)
IntegrityError: null value in column "bank_account_id" violates not-null constraint
CONTEXT:  SQL statement "UPDATE ONLY "public"."account_bank_accounts_wizard" SET "bank_account_id" = NULL WHERE $1 OPERATOR(pg_catalog.=) "bank_account_id""

2013-01-30 13:22:45,816 6483 ERROR demo001 openerp.sql_db: bad query: delete from wizard_multi_charts_accounts where id IN (1)
Traceback (most recent call last):
  File "/opt/openerp/server/openerp/sql_db.py", line 227, in execute
    res = self._obj.execute(query, params)
IntegrityError: null value in column "bank_account_id" violates not-null constraint
CONTEXT:  SQL statement "UPDATE ONLY "public"."account_bank_accounts_wizard" SET "bank_account_id" = NULL WHERE $1 OPERATOR(pg_catalog.=) "bank_account_id""

2013-01-30 13:22:45,816 6483 ERROR demo001 openerp.addons.base.ir.ir_cron: Call of self.pool.get('osv_memory.autovacuum').power_on(cr, uid, *()) failed in Job 1
Traceback (most recent call last):
  File "/opt/openerp/server/openerp/addons/base/ir/ir_cron.py", line 132, in _callback
    method(cr, uid, *args)
  File "/opt/openerp/server/openerp/addons/base/ir/osv_memory_autovacuum.py", line 31, in power_on
    model._transient_vacuum(cr, uid, force=True)
  File "/opt/openerp/server/openerp/osv/orm.py", line 5191, in _transient_vacuum
    self._transient_clean_rows_older_than(cr, self._transient_max_hours * 60 * 60)
  File "/opt/openerp/server/openerp/osv/orm.py", line 5155, in _transient_clean_rows_older_than
    self.unlink(cr, SUPERUSER_ID, ids)
  File "/opt/openerp/server/openerp/osv/orm.py", line 3976, in unlink
    'where id IN %s', (sub_ids,))
  File "/opt/openerp/server/openerp/sql_db.py", line 162, in wrapper
    return f(self, *args, **kwargs)
  File "/opt/openerp/server/openerp/sql_db.py", line 227, in execute
    res = self._obj.execute(query, params)
IntegrityError: null value in column "bank_account_id" violates not-null constraint
CONTEXT:  SQL statement "UPDATE ONLY "public"."account_bank_accounts_wizard" SET "bank_account_id" = NULL WHERE $1 OPERATOR(pg_catalog.=) "bank_account_id""